Syrian first responders discovered the largest Islamic State (ISIS/ISIL) mass grave so far, holding at least 3,500 bodies and located outside Syria’s city of Raqqa, once the de facto capital of the terrorist group’s nearly completely fallen self-declared caliphate, a local forensic assistant revealed on Thursday.

“These are individual graves, but behind us, by the trees, are the mass graves of those executed by Daesh [ISIS],” Asaad Mohammad, a 56-year-old forensic assistant at Raqqa’s al-Fukheikha agricultural suburb housing the grave, told the Agence France-Presse (AFP) agency.

“There are some 2,500-3,000 bodies estimated there, plus between 900 and 1,100 bodies in the individual graves, so at least 3,500 total,” he also said, adding, “Al-Fukheikha is the largest grave since IS [Islamic State] came to Raqqa” in 2014.

AFP acknowledged that investigators have identified eight other mass graves in and around Raqqa, including one nicknamed “Panorama” that contained over 900 bodies.

The Rapid Response Division of Raqqa’s civil defense service — charged with excavating the sites in the region — learned of the mass grave in al-Fukheikha last month, more than a year after U.S-backed forces seized the area from ISIS.

AFP notes, “The belated discovery is the biggest example yet of how the violence IS sowed during the reign of its ‘caliphate’ will be harvested for years to come.”

Under U.S. President Donald Trump’s watch, the U.S.-led coalition and its local allies have reduced the so-called caliphate that once sprawled across a third of Iraq and Syria into a hamlet of tents pitched in an ever-shrinking tiny pocket of territory in the Syrian village of Baghouz.

Mohammed predicted that authorities will likely find more graves in and around ISIS’s last bastion in Baghouz, home to fierce fighting between U.S.-backed local fighters and the jihadis.

“The same thing that happened here will have happened there,” he told AFP. “Maybe it’s even worse there, because the fighting is more intense as they’ve got nowhere else to go.”

Since January 2018 alone, the Raqqa first responders division has exhumed more than 3,800 bodies, Turki al-Ali, the force’s supervisor, told AFP.

Of the 3,800 bodies exhumed since January 2018, investigators were only able to identify 560 who were subsequently handed over to their families for a proper burial, the supervisor revealed.

“No matter how much we try to deny it, the work against ISIS is by no means over. It’s likely the hard work is just starting,” Sara Kayyali of Human Rights Watch (HRW) told AFP, echoing independent and U.S. government assessments.

While acknowledging that ISIS controls less than one percent (about one square mile) of the territory it once held in Iraq and Syria, the Pentagon’s inspector general noted this month, “ISIS remains a potent force of battle-hardened and well-disciplined fighters that ‘could likely resurge in Syria’ absent continued counterterrorism pressure.”

U.S. President Donald Trump announced plans late last year to pull out U.S. troops from Syria, stressing that the 5,000 United States forces in neighboring Iraq are expected to remain with the ability to go into Syria if necessary.

Some U.S. officials have suggested a residual American force may remain in the country.