(AP) -- The officers said Saturday the U.S. forces had thought the victims in the al-Baghdadi area were militants.

An investigation is underway.

The incident came after U.S.-backed Iraqi forces earlier Saturday arrested an Isis group operative at his home, the officers said. At the time of the raid, a man in a nearby house tossed a grenade at the troops who returned fire, injuring him and his wife.

The officers spoke on condition of anonymity because they were not authorized to speak to media.

(File photo: AFP)