U.S.-issued military equipment, to include as many as nine M1A1 Abrams tanks, fell into the hands of Iranian-backed militias during the turbulent period that swept Iraq as it battled the Islamic State, the Pentagon confirmed Wednesday.

In the Defense Department Inspector General’s quarterly report, the State Department acknowledged the loss of the vehicles to the Popular Mobilization Forces, or PMF, which are primarily Shiite militias strongly connected to Iran but sanctioned by the Iraqi government.

Eric Pahon, a Pentagon spokesman, told Military Times that DoD has not provided defense equipment to the PMF.

“However, we have discovered incidents where some U.S.-origin equipment, including M1 Abrams tanks, came into the possession of certain PMF groups,” Pahon said. “This equipment was subsequently used by these groups in the fight against ISIS.”

Regardless, “all of these tanks were recently returned to Iraqi Security Forces custody,” he added.

The DoD IG’s report notes that the State Department “pressed the Iraqi government to prioritize the return of defense articles provided by the United States as designated in the sale agreements.”

Pahon also pushed back against reports that Abrams manufacturer General Dynamics suspended its contracted support to Iraqi Security Forces over the lost tanks, stating that the “Abrams maintenance program for the Iraqi Security Forces remains active.”

Official acknowledgment of the tanks’ whereabouts lends credence to reports that depicted western tech as a pivotal part of the battle to retake Kirkuk from Kurdish peshmerga forces in October.

The Iraqi convoys that descended on the city were led by Abrams tanks, followed by Iranian-backed PMF in U.S.-armored Humvees and trucks, according to Ben Alexander, an American volunteer with the peshmerga.

“You can’t take out an Abrams with anything they have over here. The peshmerga don’t make IEDs [improvised explosive device] or VBIEDs [vehicle borne IEDs], so they’re shit out of luck for Abrams,” Alexander said in an interview with Military Times after the battle.

The Iraqi government retook Kirkuk in response to the Kurdish region’s independence vote on Sept. 25. The incident stoked debate at the Pentagon about ending U.S. military assistance to Iraq.

The Abrams tanks were sold to the Iraqi government for use by the Iraqi Army as part of the Foreign Military Sales program over the past decade, Pahon explained.

“The U.S. Departments of State and Defense cooperate closely to ensure the responsible transfer of equipment and training to host-nation forces in Iraq,” he said. “We will continue to screen and vet all forces that receive U.S.-origin defense equipment and conduct end-use monitoring in order to ensure that this equipment remains in the possession of the designated end-user.”

“We continue to stress to the Government of Iraq, as we do to all allies and partners, their obligation to maintain U.S.-origin equipment under the operational control of the designated end-user,” Pahon added.

Since 2005, the U.S. government has approved more than $22 billion worth of foreign military sales to Iraq, according to the State Department. The Iraqi Government financed the majority of these arms sales through their own national funds.