A member of the Iraqi forces checks a mass grave they discovered Nov. 7 in the Hamam al-Alil area, which the Islamic State used to hold. (Ahmad Al-Rubaye/AFP/Getty Images)

— There are bodies here and they were dumped on piles of trash in a windswept field of dirt at the edge of a small Iraqi town that until two days ago had been occupied by Islamic State fighters.

Other things were less clear.

The latest mass grave in a series of mass graves left behind by captured, retreating or dead Islamic State militants was discovered Monday. Iraqis expect that many more clandestine burial sites will be found in the coming weeks as Iraqi forces take more territory from the Islamic State.

The identities, cause of death and even the number of bodies left behind at the outskirts of a bombed-out agricultural college on the outskirts of Hamam al-Alil were unknown.

The Iraqi federal police on Monday said 100 corpses were found. A team of investigators in an hour’s time on Tuesday uncovered 20, maybe 25.

It was hard to tell, they said.

“The dogs got at them,” said Dhargam Kamil, the director of the mass graves unit at the Al Shuhada Foundation in Baghdad.

How did the victims die?

That would have to await forensic teams, too. They were still searching for bodies but were unsure if land mines had been laid in the area.

Initially the Iraqi military suggested the bodies had all been decapitated. But the evidence did not support the early claim. Two corpses had been pulled from the top of a trash pile. One had been decapitated; the other not.

“There was evidence of torture,” said Muhammad Tahir Al Tamimi, an official from Iraqi Prime Minister Haider al-Abadi’s office.

The investigators from Baghdad said some of the bodies had been bound at the wrists and ankles. Some were blindfolded. They assumed most were probably shot.

“They were killed by ISIS in acts of revenge,” Kamil said. “In very brutal ways, it appears.”

Dumping the bodies like this was also a part of the punishment,” he said. “Their message was that these men did not deserve a proper burial, that they were thrown out like trash.”

Locals told Iraqi federal police that over the past three weeks Islamic State fighters have been rounding up former members of Iraqi security forces.

The investigators said, based on the state of decomposition, the bodies were probably dumped in the last few weeks.

In the center of recaptured Hamam al-Alil, neighbors brought two Washington Post reporters into a villa they say had been used as a kind of courthouse, interrogation center and jail. In darkened rooms on the second floor, there were five numbered makeshift cells with heavy metal doors. The cells were tiny, with just enough room for a man or two to stand.

Over the last three weeks, since the Iraqi offensive to retake Mosul began, the Islamic State brought men bound and blindfolded into the building, said Hussein Ahmed Sayir, 19, who lives across the street.

“They tortured them,” he said. The teenager said the neighbors could hear screams at night.

The locals here said they think that some of these men probably ended up in the mass grave outside of town.

An Iraqi police intelligence officer stopped by the house and confirmed that it was used as a jail.

A United Nations human rights organization on Tuesday charged that Islamic State fighters recently abducted 295 former Iraqi security forces members from towns and villages to the south and west of the ISIS stronghold in Mosul.

The militants also forced 1,500 families to retreat with them from Hamam al-Alil to the Mosul airport, where U.N. officials fear they will be deployed as human shields.

“People forcibly moved or abducted, it appears, are either intended to be used as human shields or — depending on their perceived affiliations — killed,” said Ravina Shamdasani, spokeswoman for the U.N. High Commissioner for Human Rights, during testimony in Geneva, according to Reuters.

Previously, the United Nations group said it had gathered reports that 50 former police officers were executed in Hamam al-Alil last month. It is possible that some of these men are at the mass grave.

Villagers in the surrounding area have said that Islamic State militants rounded up men at gunpoint as Iraqi forces advanced and made them walk to Hamam al-Alil.

Some who later escaped said that former police and army officers were separated from them and summarily executed as the militants grew suspicious they were collaborating with the advancing Iraqi forces.

Loveday Morris in Irbil contributed to this report.