A tank of Iraqi security forces is seen during a battle with Islamic State militants in Ali Rash, southeast of Mosul, Iraq Nov. 5, 2016. Reuters

An Islamic State group weapons factory has been discovered by the Iraqi military in a town that is a forty-minute drive south of Mosul called Hammam al-Alil. The plant supplied the terrorist group with hundreds of mortar shells and missiles, Russian state media reported Wednesday.

The weapon making facility was found inside of a residential home that was abandoned by the family that owned it when the militant group also known as ISIS captured Mosul in 2014.

Iraqi forces also discovered this week a mass grave of hundreds of dead bodies in Hammam al-Alil in the wake of the Iraqi military gaining territory in their campaign to recapture Mosul from ISIS control and liberate cities along the way, BBC News reported. More than 30,000 Iraqi and 4,000 Kurdish fighters are participating in the U.S. backed offensive to recapture Mosul, Iraq’s second largest city and the last major urban stronghold within the group's proclaimed “caliphate.”

An Associated Press video of Iraqi security forces excavating the mass gravesite in Hammam al-Alil showed all of the dead bodies had been decapitated. In the video, a soldier can be seen holding up a child’s stuffed toy among the sea of corpses.

The mass grave was found by Iraqi forces on the property of an agricultural college, Reuters reported. A member of the Nineveh provincial council, Abdul Rahman al-Waggaa, said the town’s college had been used as a “killing field” for hundreds of people before the Iraqi military freed the city last weekend.

ISIS had at one point a massive arsenal that included U.S.-made weapons stolen from Iraqi army and Syrian opposition groups, an Amnesty International report in December found. The weapons cache involving assault rifles, tanks and anti-aircraft defense systems designed or manufactured in 25 countries, "ultimately reflects decades of irresponsible arms transfers to Iraq and multiple failures by the U.S.-led occupation administration to manage arms deliveries and stocks securely, as well as endemic corruption in Iraq itself," the report included.