WASHINGTON (AP) – The military has opened a criminal investigation into a November 2005 firefight between U.S. Marines and insurgents near Baghdad that left 15 Iraqi civilians dead, defense officials said Thursday.

The inquiry will determine whether the Marines involved in the firefight in Haditha acted appropriately when they fired on the civilians following a roadside bomb attack, said a military official who requested anonymity because the investigation has not been announced yet.

Military officials in Iraq completed a preliminary investigation and have forwarded it to the Navy Criminal Investigative Service. Several defense officials acknowledged the investigation is taking place, though the details were provided by one official.