Iraqi forces say they found a mass grave with about 500 bodies near a prison in Mosul. The victims are thought to be “civilian prisoners” killed by the Islamic State, members of the Hashd al-Shaabi forces said Saturday. The mass grave was found at the Badoush prison, where the terrorist group slaughtered hundreds of inmates when it took over Mosul in 2014. The prison was liberated by Iraqi forces on Wednesday, though it was not clear if they found anyone currently in detention there. An army source who accompanied the Hashd forces in the area did not confirm the discovery of a mass grave, and the claim could not be immediately verified. The report does seem to match with a 2014 report by Human Rights Watch, however. In the report, the group cited survivors of the IS takeover who said about 1,500 inmates of the Badoush prison were rounded up and taken to an isolated area in the desert. The report also said IS gunmen executed Shia inmates after separating them from Sunnis and Christians. In February, Iraqi forces discovered about 4,000 bodies in another mass grave along the Baghdad-Mosul highway. The terrorist group had used the massive Khasfa sinkhole to dump the bodies of its “enemies,” making it the largest mass grave uncovered in the area so far.