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After he fled from this tiny northern Iraqi hamlet four months ago, Hayder Khalef got panicked phone calls from his relatives who had remained behind. They were at that moment being led by Islamic State group gunmen toward a checkpoint on the edge of town.

"If you don't hear from us, you'll find our bodies near the checkpoint," Khalef said they told him in the calls.

He is back in his hometown for the first time since, after Iraqi Kurdish fighters last week drove out the extremists holding the village. Khalef and a few other residents who escaped followed the Kurds in, hoping to discover what happened to hundreds of their relatives and neighbors who vanished after the jihadis overran Hardan in early August.

They fear they know where they are: four mounds of recently dug-up earth. The sites have not yet been excavated, but Khalef and others are convinced they are mass graves, possibly holding dozens of dead. From the loose top soil, they and Kurdish fighters pulled out pieces of clothing as an Associated Press reporter watched.

At one point, they tugged on the elastic waistband of pants visible in the dirt — and it seemed a body was still wearing them. The ground bulged with the weight of a body being pulled up with the waistband. They stopped pulling, fearing booby traps, before a body could be clearly seen. But an ID card and some prayer beads fell out of the pants pocket — the ID of a 44-year-old man named Khero Khudeda Rufo. One returning resident, Khaled Wase, recognized the name as a neighbor who is among the missing.

There is no way to definitively say the mounds are graves or know how many bodies are in them until they are dug up. The Kurds have no plan to do so immediately, though they have cordoned off the four sites with tape. Fighting continues with Islamic State militants not far away, and the situation is too unstable to deal with searching for bodies. But Wase and Khalef say they are certain their loved ones are buried in the sites.

"They are all from my village and some of my cousins were arrested (by the militants) and may be here," Wase said, referring to the earth mounds. "My relatives are there along with all those from my village." Wase and Khalef estimate that some 530 people are missing from Hardan, out of an original population of about 200 families, and he believes most were killed by the militants.

Hardan is one of a number of tiny villages dotting the plains of northern Iraq populated by members of the Yazidi religious community. When the Islamic State group swept through the area in early August, its fighters unleashed some of their most brutal atrocities against the Yazidis — whom they consider heretics. Hundreds were killed, and the militants abducted hundreds of Yazidi women and girls, enlisting them as sex slaves given to their fighters and supporters, according to accounts by escaped women and reports collected by the U.N. and rights groups.

On Aug. 3 — the same day they took the largest town in the area, Sinjar — the militants appeared at the entrance to Hardan in eight black SUVs, backed by Sunni Muslims from neighboring villages, Wase recounted. They ordered residents to hand over any weapons they possessed or else the extremists would behead their families, Wase said. The residents complied. Some fled that very night, including Wase and Khalef. Others were unable to leave, however, and stayed, hoping for the best, they said.

Wase said he made his way across the nearby Syrian border. He too received phone calls from relatives saying they were being taken by the militants toward a checkpoint on the side of town. He and Khalef said they were told about 150 people were taken to the checkpoint. What happened next is unknown, but both men believe all were killed.

Khalef said he also got a call from one of his cousins who hid in the village and saw the families being marched to the checkpoint and later saw an earthmover digging in the nearby fields. "My uncle and two of his sons along with 50 others I know from Hardan" are among those missing, Khalef said.

Iraqi Kurdish peshmerga fighters recaptured Hardan on Friday, and a handful of Yazidi residents quickly followed to search for loved ones. They found three of the mounds in a field. Wase said he found a headband and scarf he recognized as belonging to his relatives in one mound. At a spot about 100 meters (yards) away, the earth was scorched and littered with clothing, womens' shoes and a baby's pacifier.

The fourth site was found Sunday when the peshmerga were setting up a position and digging a latrine, and they noticed clothes in the dirt. It was there that they tugged at the half-buried pants that appeared to still be on a body.

Sammy Tahar, a 44-year-old peshmerga fighter, said he too believes the mounds are graves. "This is the worst of Daesh and the terrorists," he said, using the Arabic acronym for the Islamic State group. "They brought these innocent people who were just minding their own business and they killed them."