More than 500 bodies were exhumed last week from one of the largest mass graves in Raqqa, Syria, once the de facto capital of the Islamic State (IS) terror group.
A local team of first responders has been carrying out the exhumation of mass graves in and around Raqqa since U.S.-backed forces liberated the city from IS in October 2017.
"So far, we have worked on seven out of 10 mass graves that have been discovered in Raqqa," said Yasir Khamis of the Raqqa Civil Council, which is responsible for running the city.
"This is one of the largest mass graves in Raqqa. It took us three months to finish the work here. Some of the bodies we found belong to IS fighters, but others belong to civilians, including children and women," he told VOA.
WATCH: Hundreds of Bodies Exhumed From Raqqa Grave
During its brutal reign in Raqqa, between 2014 and 2017, IS carried out mass executions of locals who opposed it or did not adhere to its extremist ideology.
Local experts said about 1,500 more bodies were thought to have been buried at the Panorama mass grave, named after the roundabout where it was found.
Rights groups have demanded the preservation of bodies and evidence for possible war crimes trials.
"We are in a race against time. These bodies are decomposing at an exponential rate," said Sara Kayyali, a Syria researcher at Human Rights Watch.
"If these bodies are not preserved in the correct way, in the way that's been established, then it does mean that much of this evidence might be lost when we're seeking accountability for crimes committed either in the context of the battle or before it," Kayyali told The Associated Press.
Bodies found at the Panorama grave are believed to have been buried there in the last days of the four-month campaign to liberate Raqqa from Islamic State.
Experts say they also are carefully examining the bodies to determine the possible identities of IS fighters.
"We look into whether these [IS] fighters are local and foreign," Mahmoud Haji Hassan, a local forensic doctor, told VOA.
"We can differentiate between local and foreign fighters by their body attributes, face features and types of hair," he added.
More mass graves are expected to be found in Raqqa and elsewhere in Syria and Iraq, where IS's so-called caliphate once existed.
Mass graves left behind by IS exemplify the challenges that face stabilization efforts in areas liberated from the terror group.
Local groups working in this field do not receive the support they need in terms of expertise and workers, analysts say.
"To accelerate the process, your need more resources to help workers and experts in exhuming and examining the bodies," Munjid Issa, a local reporter who closely follows the developments in Raqqa, told VOA.
"This is a complex project that requires more tangible support from the international community," he said.