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 Isis 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.
Over the last three weeks, since the Iraqi offensive to retake Mosul began, Isis brought men bound and blindfolded into the building, said Hussein Ahmed Sayir, 19.
"They tortured them," he said. The teenager said the neighbours 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.
A United Nations human rights organisation yesterday charged that Isis 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 1500 families to retreat with them from Hamam al-Alil to the Mosul airport, where UN officials fear they will be deployed as human shields.
Previously, the UN 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.