BAGHDAD (AP) — Iraqi authorities said Saturday that they were investigating an explosion that struck a base belonging to the Popular Mobilization Forces, a coalition of Iran-allied militias, killing one person and injuring eight.

Militia officials had initially described the explosion at the Kalsu military base north of Babylon — a former U.S. base that was handed over to the Iraqi military in 2011 — as an airstrike, blaming it on U.S. forces. The U.S. Central Command denied in a statement that it had carried out any airstrikes in Iraq.

The PMF in a statement Saturday afternoon described the blast as an “attack” but did not blame any specific party.

Iraq’s Security Media Cell said the country’s air defense command had not detected any drones or fighter plane in the airspace of Babylon before or during the explosion. It said one PMF member died and eight people were injured, including an Iraqi army soldier.