On an arid hillside high above this now infamous city, Margarita Isidoro tirelessly wields a machete in search of her son.

The petite 57-year-old wearing black and pink sneakers, and a purse slung across her shoulders, moves with single-minded focus. She hacks at tangles of a thorny shrub and crawls into crevasses in the uneven terrain, driving her blade again and again into the soil. She kneels, claws at the dirt and tosses rocks aside.

Isidoro isn't alone. Emboldened by international attention on 43 disappeared college students, dozens of parents have come out to hunt for their own children who have been missing for months or even years, digging alongside Isidoro as they'd never dared before, and as authorities never bothered to do.

"Whether he is dead or alive, I want to find my son," says Isidoro, whose youngest went missing in April 2010.

Isidoro was afraid to search before now because someone had warned her that the same people who took her son in the badlands of the southern state of Guerrero might come after her or the rest of her family. Her son Orlando Catalan was 22 years old when he left home one afternoon to buy water and never returned. His car was found in another neighborhood eight days later. "Now I'm ready, if they take me, they take me. I'm going to find my son."

More than 22,300 people have gone missing in Mexico in the past eight years by the government's count, a number that human rights activists believe to be much higher given the expanses of the country controlled by organized crime. Among the disappeared are the 43 students from the Rural Normal School of Ayotzinapa, who were taken by Iguala police Sept. 26 and allegedly turned over to members of the Guerreros Unidos drug gang that rules parts of the state. The Mexican government says the students were likely killed and their bodies incinerated beyond identification. The mayor of Iguala and his wife were arrested and accused of complicity in the mass crime.

After the 43 students vanished, searches around Iguala turned up at least 10 secret graves. None of the remains found in those mounds proved to be the students, but knowing they belonged to someone's son or daughter, more relatives came forward to seize the moment.

The parents out searching the rugged terrain on this late fall Saturday have banded together in a shared fury over government involvement in the deaths of the Ayotzinapa students, and a suspicion that officials could have been involved in the disappearances of their children, too. What gives them the courage to search for the bodies now, they say, is that federal police have agreed to guard the area, and international journalists are there as witnesses.

Still, they are afraid as they pile into trucks and drive miles over rocky roads up into the hills for the second consecutive weekend. The relatives, and even the priest on hand to celebrate Mass before the search, tape paper over their license plates to make it more difficult to identify their vehicles. In the brush they don't call out to each other by name, instead shouting for "the friend with the red handkerchief."

A week earlier, family members had unearthed suspected graves and, in some cases found human remains. This time, under a new agreement with the attorney general's office, they only identify suspicious spots, planting small orange flags or leaving piles of stones as markers where federal investigators should excavate.

"For us, all of Iguala is a clandestine cemetery," said Claro Raul Canaan Ramirez, whose sons, 21-year-old Hiram Jafeh Canaan Avila and 24-year-old Omar Canaan Avila, disappeared Aug. 30, 2008, in Iguala. A cousin and an acquaintance with them were killed.

Canaan says locals led them to hillsides with suspected graves. He explains how he looks for depressions in the ground that are more or less the size of a body. He and the others probe for soft soil with steel rods, sometimes pulling them out and sniffing the tips. Beer bottles or signs of campsites could be another clue, because victims may have been held there before burial. Don't be dissuaded by rocks, they say, because at other gravesites, stones were piled atop the remains.

Previously, "I searched, but in my own way, by my own means," Canaan said. "But really when it's just one person against the world it is almost impossible."

After returning to their base at an Iguala church on Saturday, Canaan struggled to find volunteers to work the coming week. Each day they need someone at the church to speak to newly arriving relatives, and four or five others to accompany federal investigators into the mountains. Some relatives complain that they are tired and that a small number are shouldering too much of the burden, ignoring responsibilities at home. They say many other families came to the church for information, gave DNA samples and filed reports with authorities, but have not returned to help.

The relatives are angry that they must search for the missing themselves, yet they fear this chance to do so is fleeting, and don't want to let it pass.

"I have a lot of fury, a lot of hatred," said Maria Ines Roman Sandoval, who is looking for her 17-year-old son Marco Antonio Mendez Roman.

Since he disappeared in April 2013, Roman has sold nearly everything she owned — her stove, gas tank, bed, chickens and corn — and moved in with relatives in a crowded home on the outskirts of Iguala, where freshly made holiday pinatas hang on the patio to dry. Now, Roman bends to clear rocks and poke the ground with her long stick, hoping to find something she can identify as her son's.

"I know his shoes. I know the shirt he was wearing. I know the pants he had on too," she says. "I am going to keep searching, I have to find answers."

For many, the digging follows months of combing hospitals, jails and morgues, and sometimes years of false hope.

Guillermina Sotelo Castaneda's farmworker son Cesar Ivan Gonzalez disappeared on Aug. 19, 2012 after driving her from Huitzuco, a town about 45 minutes from Iguala, to Cuernavaca. She never saw him again, although she still pictures him leaving for work in the morning with a small water jug slung over his shoulder, a backpack and a machete. She sees him coming through the front door with armfuls of tomatoes, squash or limes, whatever he had harvested that day.

Months after filing the initial report of his disappearance, she went back to police to find they had no record of the case. She and her husband have lived the U.S. for more than a decade, but send family members to the local morgues in Chilpancingo, Iguala and Cuernavaca anytime unidentified remains show up. So far, none belong to her son.

Two weeks ago, after watching news reports of bodies discovered in the mountains around Iguala, Sotelo, 54, bought a one-way ticket from her home in North Carolina back to Mexico to resume her search.

Even as she digs in the dirt for her son's remains two years after he disappeared, Sotelo admits that she continues to make payments on a motorcycle he bought, because she knows how much he loved it and because it would break her heart if it was repossessed. And as long as this opportunity to search lasts, Sotelo says she will continue. In her mind, until she can bury her son he is still alive.

"One has to overcome the fear, because if not who is going to look for our children?" Sotelo said.