Updated

The military has opened a criminal investigation into firefight between U.S. Marines and insurgents last year that left 15 Iraqi civilians dead, defense officials said Thursday.

The inquiry will attempt to determine whether the Marines acted appropriately when they fired back at insurgents following a roadside bomb attack in Haditha, near Baghdad, in November 2005, said a military official who requested anonymity because the investigation has not been announced yet. The civilians were hit during that battle.

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

According to the official, the initial allegations of possible violations were brought to the attention of the military by a reporter in mid-February.

Fifteen Iraqis, eight insurgents and a U.S. Marine were killed in the incident, which began when a roadside bomb detonated next to a joint Iraqi-U.S. squad patrolling Haditha. Immediately after the explosion, insurgents attacked the patrol with small arms, sparking the firefight.

The Marine killed was assigned to Regimental Combat Team 2 of the 2nd Marine Division, two other Marines were injured. Defense officials Thursday would not identify the unit or Marines involved in the investigation. While several Iraqis were part of the patrol, they are not involved in the investigation, the official said.