WASHINGTON (AP) — The Pentagon says the two Army Rangers killed during a raid on an Islamic State compound in Afghanistan may have died as a result of friendly fire.

Navy Capt. Jeff Davis says the U.S. military is investigating to see if they were accidentally killed by ground fire from Afghan commandoes or other American forces. He says it does not appear deliberate.

He says the head of the IS affiliate in Afghanistan was the target of the Wednesday raid. Officials suspect he was killed but haven't confirmed that. About 35 other enemy fighters were killed.

Davis says 50 Army Rangers and 40 Afghan commandos took part in the assault on the compound and faced a fierce, three-hour firefight. The Rangers were killed in the initial minutes of the fight.