The small copper horseshoe Mario Vergara Hernández keeps in the pocket of his jeans isn’t there for good luck. It has another purpose altogether. “Since I started looking for graves, I carry this horseshoe in my pocket, because if they find me in a common grave, the metal won’t disintegrate,” said Vergara Hernández, palming the charm as we sat beside a hole he was helping to dig. “I told my mother that if I disappear, she should tell the government to look for the metal. I just hope they bury me with my pants on.”

With that, he stood and declared that the hole he and two other men—both of them fathers whose sons had been disappeared—were digging didn’t contain any corpses. With pick and shovel, they had dug to a level of clay that was undisturbed; there could be nothing buried further beneath it. While the men dug, the women waited under a tree, a light breeze relieving the near-100-degree heat and extreme humidity. They had come to this spot after a tip by a local drug runner, who said his own family members had been secretly buried near a large tree in a field outside of the city of Iguala, in the southern Mexican state of Guerrero.

Every Sunday, Vergara Hernández leads a group organized under the name Los Otros Desaparecidos de Iguala (The Other Disappeared of Iguala) into the hills surrounding the city. They’re akin to a self-taught search team, comprising family members of people who have been disappeared from the region. The group works off hand-drawn maps, messages on WhatsApp and Facebook, and tips from folks who, somehow or another, have seen bodies being buried late into the night. When we arrive at the site the searchers fan out, expertly scanning the ground, looking for upturned soil or disturbed plants as they hunt for mass graves, with the hope of identifying a loved one.

Los Otros Desaparecidos de Iguala came together after the infamous disappearance of 43 students by local police in concert with local paramilitaries two years ago, on September 26, 2014. But it wasn’t until the discovery of 38 bodies in the weeks following the disappearances that the media storm began. As grave after grave was turned up outside of Iguala, Argentine forensic experts identified the remains of Alexander Mora Venancio, one of the 43 students. The other 42 young men are still disappeared.

The bodies kept coming as mounting protests against the mass disappearances brought out more and more family members from Iguala. “The tragedy of the 43 happened, here in Iguala, and the parents held marches, and my sisters went and said that they too are missing their brother,” said Vergara Hernández, whose brother Tomás has been missing since July 5, 2012. “There, they met more families who brought photos of their disappeared family members, and that is how Los Otros Desaparecidos de Iguala was formed.” Since they started searching in November of 2014, the group has found 145 bodies. Sixteen of them have been identified and returned to their families for burial.

The plight of the 43 missing students from the Ayotzinapa Normal School has captured the world’s attention, with high-level investigations and ongoing public demonstrations demanding their return alive. The Mexican government continues to say the students were killed and their bodies burned in a garbage dump near Iguala, a claim thoroughly discredited by international experts. To this day, there is no convincing explanation of where the 43 students might have been taken after they were disappeared. This has translated into a serious crisis of legitimacy for all levels of government in Mexico. During this national institutional crisis, the work of self-trained searchers has quietly proliferated throughout the country. Their work is a response to the spectacular violence that has accompanied the US-backed war on drugs in Mexico.

It takes some measure of imagination to comprehend the reach and intensity of drug-war violence in Mexico. In 2014, Mexico ranked as the country with the third-most civilians killed in internal conflict, after Syria and Iraq. Bodies have been buried, burned, displayed in public places, hung from bridges and overpasses, or beheaded and left at city hall. The lifespan of Mexican men has fallen due to the increase in homicides since the war on drugs began in December 2006. Hundreds of thousands of people have been displaced because of violence, from urban areas and rural ranches alike.

Much of the violence and terror is state directed. Drug cartels, which operate more like paramilitary groups, are often indistinguishable from local and state police, and form networks dedicated to extortion, kidnapping, and killing, all of which increases social control and helps to suppress dissent. Militarized federal police carry out offensives, supposedly against drug traffickers; where they do so, overall homicide rates have tended to rise. The army has been deployed to fight drug trafficking, in what Dr. Richard Downie of the National Defense University in Washington, DC, says has led to “the best US/Mexican military-to-military and defense relations in decades.” The New York Times reported in May that Mexican soldiers kill eight people for every one they injure; the kill rate for the Mexico’s Marines is 30 to 1.

When it comes to disappearances, official numbers are staggering—but they represent a fraction of the total. According to the Mexican government, as cited by Amnesty International, 27,638 people have been registered as disappeared or missing since 2006. Nearly half of the disappearances have taken place since December 2012, during the presidency of Enrique Peña Nieto.

Informally, it is known that the number of disappeared is much higher. The official number only counts Mexicans who have been disappeared. Advocates for Central American migrants have said tens of thousands have been disappeared in transit through Mexico, but there is no centralized record keeping. In Iguala, Vergara Hernández said his group includes over 500 families with at least one disappearance. Of those, he says, only 215 cases have been reported to police.

The situation is similar in Coahuila, whose southern border is about 700 miles north of Guerrero, where another group of searchers in the city of Torreón say state officials are underreporting the number of people disappeared by a factor of six. “They insist that there are 579 people disappeared,” said Silvia Ortíz, who leads Grupo VIDA, a search group made up of family members of people disappeared in Torreón. “But that doesn’t include those who didn’t make a complaint. There’s around 3,500, more or less, people disappeared.”

Ortíz and her husband, Oscar Sánchez de Viesca, have been looking for their daughter Stephanie “Fanny” Sánchez de Viesca Ortíz since she was disappeared on November 5, 2004. But many families choose to go on living as if nothing happened after a loved one is disappeared, for fear of further violence and direct threats from state officials if they make a formal complaint.

In Torreón, Grupo VIDA (the acronym stands for Victims for our Rights in Action) got together after they heard about the searches in Iguala. Ortiz, like many mothers with missing daughters, undertook her own search, even opening a case with the FBI after a tip that her daughter was in Texas. “I realized I wasn’t going to be able to do it alone, and when I saw the searchers in Iguala starting to look, I said, it’s now or never,” said Ortiz.

Torreón is an industrial city of just over 600,000 that’s part of a larger urban area almost exactly 500 miles southwest of San Antonio, Texas. The area was at the heart of Mexico’s cotton boom, but since the 1990s the city has followed in the footsteps of border towns like Ciudad Juárez, with low-wage manufacturing dominating the local economy. Torreón and the conjoining municipality of Matamoros were hit hard by the US-backed war on drugs. As the area was militarized, the murder rate spiked from an average of 43 killings a year from 2000 to 2007, to over 825 murders in 2012 alone.

“There was really a sensation that we lived in a very peaceful city, and in effect, we did,” said Carlos Castañón, an analyst in Torreón. We spoke in a cafe that had opened just six months prior, as people began to go out again in the city’s downtown after years of violence. “Beginning in 2007, every year afterward until 2012 was worse than the one before, which is to say each year there were more deaths, more killings, more homicides, and a significant increase in stolen vehicles, kidnappings, and extortions,” he said.

Torreón is located at a strategic crossroads between the railways and highways up to El Paso and Laredo, Texas. Local lore has it that the former governor of Coahuila, Humberto Moreira, allowed the Zetas drug cartel to enter Coahuila in exchange for huge personal gain, and it was a fight between Zetas and members of the Sinaloa cartel that led to extreme levels of violence in the city. But there are other players, as federal police and soldiers were also deployed to the city, and municipal police supervised the bulk of criminal activity.

The city became a war zone. “If you look at the kinds of weapons they used here, you’ll find grenades, bazookas, and Barretts [a 50-caliber semi-automatic sniper rifle],” said Castañón. At the height of the violence, prisoners were released from a nearby jail in Durango state at night, crossing over to Torreón and opening fire on bars, nightclubs, and parties, killing dozens at a time. The city was a war zone, and the bare, dry farmlands that surround it were transformed into killing fields.

It is into those fields that Grupo VIDA trudges every Saturday, looking for their loved ones who were swept up during the violence. Here, they don’t look for graves exactly, but for bones and bone fragments. Unlike in the south of Mexico, bodies here are rarely buried: The favorite disposal method of the killers was to mix bodies with diesel and cook them in 55-gallon drums until only shards remained.

No one knows why so many people have been disappeared in Mexico. The disappeared here, for the most part, are not political activists. Rather, they are people from poor and working-class families, and most of them are men. The government and mainstream media stigmatize the disappeared, alleging that they must have been involved in criminal activity. Family members speculate that their loved ones are being forced to work for drug cartels, or that disappeared young women are made to work in the sex trade. The only sure thing is that the state provides a total screen of impunity, a context in which kidnapping and killing can happen on a massive scale and almost always go unpunished.

And so we walk. After a tip brings the group back to a spot they call “Patrocinio” for the eleventh time, we take off in groups of two or three in all directions, scanning the desert floor. The only interruptions are a row of trees far off to our right, and a smattering of abandoned buildings on the horizon. I walk alongside Rosa Maria Flores Garcia while her 8-year-old grandson runs circles around us and her adolescent granddaughter walks quietly, preening, shading the sun with her hand so as not to upset her hairstyle with a hat.

Flores Garcia’s son Sergio Vazquez Flores, father to the two grandchildren who walk with us, was disappeared on February 1, 2010. The way Flores Garcia tells it, Sergio stepped out to buy a soda that day at around 9:30 in the morning and never came back. He was 26. “Everything ended when that happened; there’s no joy anymore,” said Flores Garcia, stopping to scoop the earth with a shovel. Flores Garcia works six days a week cleaning houses and serving tacos, for which she makes about $44. Every Saturday she joins Grupo VIDA to search for bones in the desert.

Eventually the searchers go down on their hands and knees around a spot where dozens of small, charred bone fragments are lying exposed. There’s no sniffing dogs or special protocol: The bones are lifted from the desert ground and placed into a plastic bag. Many will be too burned to carry DNA. Of the hundreds of bone fragments Grupo VIDA has turned over to authorities in the year and a half since they started their searches, not a single one has been DNA-matched.

Bottom-up strategies to locate the disappeared have bloomed as the crisis of the disappeared deepens in Mexico. Central American mothers carry out annual caravans, traveling through Mexico with photographs of their children whose last known whereabouts was in Mexico. Another group of family members of disappeared have formed a Citizen’s Forensic Science committee, collecting DNA samples from relatives of people disappeared to do the genetic testing they say the Mexican government isn’t doing.

Graciela Pérez, whose daughter Milynali Piña Pérez, as well as her brother and three nephews, was disappeared as they drove along a highway in the northern state of Tamaulipas in August of 2012, is a member of the Citizen’s Forensic Science committee. She says that when she first went to the police in Tamaulipas, their archive of photographic files of bodies found in graves in the state was kept in a Hotmail account. Pérez says state officials do little to identify the bodies they find. Each of Mexico’s 32 states has its own system for dealing with mass graves, and a maze of bureaucracy means DNA tests have to be requested individually for each body found. “Many families have been forgotten; there are thousands of bodies that haven’t been identified,” said Pérez. Her group has collected DNA samples from victims around the country and is pushing the Mexican government to run their samples against unidentified bodies buried clandestinely, as well as those buried by state officials in common graves only as NN, nomen nescio, for name unknown.

Mexican officials chronically underreport the number of bodies found in clandestine graves. In a February report to legislators, Mexico’s attorney general’s office said 662 bodies had been found in 201 graves in 16 Mexican states between August 2006 and October 2015. An analysis carried out for this story found that over the same period, newspapers reported at least 2,439 bodies having been recovered from clandestine graves in 30 of Mexico’s 31 states, as well as in Mexico City. Even this higher figure is a low estimate that depends on media coverage in places where journalists have been silenced, killed, or disappeared for covering the drug war, and it doesn’t include bodies that were displayed, not buried, or, for example, 167 50-year old skulls found in a cave in Chiapas in 2012, or 61 corpses found rotting at an abandoned crematorium in Acapulco in 2015. Nor does it include more recent horrors, such as the charred remains of 300-400 people found in Tlalixcoyan, Veracruz, in February.

In November 2015, a few weeks after the cut-off for the attorney general’s report, a mass grave created by state officials in Tetelcingo, Morelos, was uncovered by a mother searching for her son. The grave contained at least 117 bodies, which were dumped—many without having been identified or DNA-tested—near a cemetery by government workers, who claim they were too overburdened and under-resourced to properly bury the bodies. The bodies were pulled from the ground in June while family members of people disappeared looked on, hoping to identify a loved one. An independent report released in August found that 84 of the 117 bodies showed signs of violence and torture, and that only eight of the bodies were identified after the exhumations. Experts say the grave shared characteristics with clandestine graves in other parts of Mexico that were attributed to the organized crime group Los Zetas.

Through it all, families continue to search, scouring forests, deserts, garbage dumps, abandoned lots, and open areas behind cemeteries. They have been threatened by organized crime and state officials; Miguel Ángel Jimenez Blanco, who initiated the searches in Iguala, was murdered last year. “It is not easy, it’s not nice at all, to pick up a shovel or a pick and go look for my child,” said Maria de la Luz López Castruita, whose daughter Irma Claribel Lamas López went missing in Torreón in 2008. López Castruita said she will continue to look for her daughter until the day she dies. “When our child disappeared, so did our fear.”

This story was made possible by a grant from the Fund for Investigative Journalism.

Correction: This text was updated on April 6, 2017, to reflect the fact that Silvia Ortíz and her husband, Oscar Sánchez de Viesca, have been looking for their daughter Stephanie since she was disappeared on November 5, 2004 (not May 10, 2005).