Syrian rebel fighters say they have found around 40 bodies showing signs of torture in the mortuary of a military hospital in a suburb of Damascus following the overthrow of President Bashar al-Assad.

Video and photos showed bodies wrapped in blood-stained white shrouds piled up inside a refrigerated room at Harasta Hospital on Monday.

Several of the bodies appeared to have wounds and bruising on their faces and torsos. Pieces of adhesive tape bearing numbers and names were also visible.

“I opened the door of the mortuary with my own hands, it was a horrific sight,” Mohammed al-Hajj, a member of a rebel group from southern Syria, told AFP news agency.

He said the rebels had gone to hospital after receiving a tip from a member of staff about bodies being dumped there.

“We informed the [rebel] military command of what we found and co-ordinated with the Syrian Red Crescent, which transported the bodies to a Damascus hospital so that families can come and identify them.”

It was not clear how long the bodies had been stored at the mortuary, but they were at various stages of decomposition.

The Syrian Observatory for Human Rights, a UK-based monitoring group, says almost 60,000 people were tortured and killed in the Assad government’s prisons.

Human rights groups say more than 100,000 people have disappeared since Assad ordered a brutal crackdown on pro-democracy protests in 2011 that triggered the civil war.

A Syrian non-governmental organisation said it was likely that the bodies in Harasta were detainees from the notorious Saydnaya prison, which is just to the north of Damascus.

“Harasta Hospital served as the main centre for collecting the bodies of detainees,” Diab Serriya, a co-founder of the Association of Detainees and the Missing in Sednaya Prison (ADMSP), told AFP.

“Bodies would be sent there from Saydnaya prison or Tishrin Hospital, and from Harasta, they would be transferred to mass graves,” he added.

The discovery of the bodies came as the Syria Civil Defence, whose rescue workers are widely known as the White Helmets, announced that it had concluded a search operation for possible detainees in secret cells or basements at Saydnaya prison without finding anyone.

Five specialised teams assisted by two K9 dog units and individuals familiar with the layout of the prison checked all buildings, basements, courtyards, ventilation shafts, sewage systems, surveillance camera cables and surrounding areas on Monday, as crowds gathered there in the hope of finding their missing relatives.

“The search did not uncover any unopened or hidden areas within the facility,” the Syria Civil Defence said.

“We share the profound disappointment of the families of the thousands who remain missing and whose fates remain unknown,” it added.

The ADMSP meanwhile shared what it said was an official document, dated 28 October, saying that 4,300 detainees were being held at Saydnaya.

They comprised 2,817 judicial detainees held in the prison’s “White Building” and 1,483 detainees held on charges related to terrorism and military tribunals in the “Red Building”.

“This approximate number represents the detainees who were released at the time of the prison’s liberation,” the ADMSP said. The BBC could not immediately verify the information.

Rebel fighters entered Saydnaya prison and Harasta hospital as they advanced into Damascus over the weekend, prompting President Bashar al-Assad to step down and flee the country.

The ADMSP said in a 2022 report that Saydnaya “effectively became a death camp” after the start of Syria’s civil war in 2011.

It estimated that more than 30,000 detainees had either been executed or died as a result of torture, lack of medical care or starvation at the facility between 2011 and 2018.

It also cited released inmates as saying that at least another 500 detainees had been executed between 2018 and 2021.

ADMSP also described how “salt chambers” were constructed to serve as primitive mortuaries to store bodies before they were transferred to Tishreen Hospital for registration and burial in graves on military land.

Amnesty International used the phrase “human slaughterhouse” to describe Saydnaya and alleged that the executions had been authorised at the highest levels of the Assad government, and that such practices amounted to war crimes and crimes against humanity.

The Assad government dismissed Amnesty’s claims as “baseless” and “devoid of truth”, insisting that all executions in Syria followed due process.

On Monday night, the leader of the Islamist militant group whose offensive led to the end of Assad’s 24-year rule said former senior officials who oversaw the torture of political prisoners would be held accountable.

Abu Mohammed al-Jolani of Hayat Tahrir al-Sham (HTS) said the officials’ names would be published and repatriation sought for those who had fled abroad. Rewards would also be offered to anyone who provided information about their whereabouts, he added.