QUTAYFAH, Syria - Refrigerated trucks would come nearly every day to dump the bodies in this barren field just outside the Syrian capital, witnesses said.

It was the job of Fayad al-Hasan, 55, a cleaner in Qutayfah, 25 miles north of Damascus, to unload the dead and toss them into deep trenches carved into the dusty earth.

On his first day, he said, he wept.

“I can’t sleep at night without seeing the scene again,” he said.

The site where Hasan worked for three years starting in 2014 is one of 10 mass graves located by civil defense workers and rights organizations in the Damascus area alone since the fall of Bashar al-Assad. They know there are still more to find.

The International Commission on Missing Persons estimates there could be as many as 66 such sites across Syria, where the Assad regime sought to hide from the world the mass killing of its opponents during a nearly 14-year-long civil war. When the graves are excavated, they could begin to shed light on the fate of the more than 150,000 people who disappeared during the conflict.

They were part of a system of “state terror” that will provide evidence for future war crimes trials, said international prosecutor Stephen Rapp, who over the past week visited several mass graves in Syria, including the one in Qutayfah. Rapp, a former U.S. ambassador at large for war crimes, was working to investigate the sites with the independent, nonprofit Commission for International Justice and Accountability and the Syrian Emergency Task Force, a Washington-based group that advocates for the Syrian opposition.

“We haven’t really seen this kind of machinery of death, or anything like it, since the Nazis,” Rapp said.

Hasan led reporters to another site nearby, this one a patch of unmarked ground in a regular cemetery. He unloaded bodies here only once, he said. He said workers were ordered to shoot or poison dogs to stop them from digging up the corpses.

Hasan never spoke of his work, he said - not even to his family.

“You better dump them, or we will dump you with them,” he recalled one officer telling him. Soldiers from the Syrian army would station themselves around the perimeter of the burial site and train their guns on him as he unloaded the bodies, he said.

“People knew about it, but no one dared to speak,” said Badarin Omar, a 44-year-old rebel with Hay’at Tahrir al-Sham - Syria’s new rulers - in charge of security at the site.

The walls of Omar’s office in the nearby military intelligence headquarters were spattered with what appeared to be bloodstains. Dark brown sprays emanated from a hook screwed high into the wall.

“This is a death cell,” said the burly commander, who had returned to his hometown Qutayfah for the first time in 13 years. Places like this, he said, were the first stop for people rounded up by the government. “This is where they would arrest people and interrogate them before sending them on to the prisons.”

Assad’s government repeatedly denied torturing and killing critics in its detention centers, but the evidence uncovered by rights organizations and exposed by whistleblowers over the years is overwhelming. In 2013, a defector smuggled out a cache of 53,000 images of corpses, known as the “Caesar” photos, taken in Syria’s prisons and military hospitals.

The regime documented its killing meticulously. In Sednaya prison, the most notorious of Assad’s jails, records now scattered across the grounds point to the scale of the death that took place inside its walls.

One ledger viewed by The Washington Post showed that on one day in 2015, the names of 25 prisoners are marked as having been sent to a military hospital. The word “corpse” is written by each name. On the following day, 18 names are listed for transfer. Four are listed as injured; the remainder are marked as corpses.

“It’s part of the bureaucracy of this regime,” said Shadi Haroun, program manager for documentation and collection at the Association of Detainees and the Missing in Sednaya Prison. “We are dealing with atrocities and arbitrary detention; all of that was subject to the bureaucratic process.”

After they were logged at military hospitals, he said, many of the bodies were dumped in mass graves such as the one at Qutayfah.

It was estimated to have held “thousands” of bodies before some were removed starting in 2019, he said. It’s unclear where they were moved. The wall that rings the three-acre site was constructed to conceal the work, he believes, or to hide the disturbed earth from researchers who studied satellite imagery for clues.

“No one is sure” why the bodies were moved, Haroun said.

Experts say the work of excavating the graves and identifying the dead will take years, if not decades. Nearly 30 years after the Srebrenica massacre during the Bosnian civil war, Rapp said, victims are still being identified and laid to rest.

Evidence at a suspected mass grave in Najha, south of Damascus, suggests recent use. A deep trench is cut into the ground. At one end it is partially filled, with scraps of clothing poking out of the rocky earth.

“It’s new, that’s why it smells,” said Mustafa Khalid, 51, who said he worked on a construction site nearby and could see the refrigerated trucks arrive. “Four days before the fall of the regime, they were here,” he said of the trucks. Like so many Syrians, he is haunted by the disappearance of a family member. His brother was stopped at a checkpoint in 2011 and was never seen again.

Since rebels swept into Damascus two weeks ago, desperate relatives have rushed to prisons and morgues, hoping to find some trace of their missing loved ones. In desperation, some have broken into graves; human rights organizations have urged Hay’at Tahrir al-Sham to secure the burial sites.

But civil defense workers have limited capacity, Omar said. He said more international assistance is needed.

Civil defense workers have already recovered hundreds of bodies from military hospitals and other sites in Damascus that were still awaiting burial. Thirty-five bodies were delivered last week to the morgue in the capital’s Mujtahid Hospital, where family members scanned the gaunt, deformed faces of the dead.

One woman vomited. Other relatives screamed, or wept silently. Some of the corpses recovered showed evidence of abuse, said Mohammed Jafran, head of forensics, including “signs of dehydration and malnutrition.”

Khadija Ali Mohammed, 44, was looking for her son, who was arrested in 2014 when he was 18. He had taken photos of the family’s destroyed house in Moadamiya, a suburban district of Damascus that was besieged and bombarded during the civil war. A former neighbor reported him, she said.

Mohammed checked the 15 remaining unidentified bodies to see if she recognized her son, who would now be 28. She did not. “Where are the bodies?” she cried.

previous coverage

• Kurdish-led forces push back Turkish-backed Syrian rebels in a tense offensive

related stories

• Cyprus can help rid Syria of chemical weapons and search for its missing, Cypriot top diplomat says