Four Marines previously listed as missing have been confirmed as killed in fighting northwest of Nasiriyah, the U.S. Central Command said Monday.

The men, of the First Marine Expeditionary Force, were killed March 27 as their M1A1 tank crossed a bridge over an Iraqi river, according to a preliminary U.S. military investigation.

The driver was shot and killed, and the tank went off the bridge and fell into the into the river upside-down. The three other crewmen apparently drowned. The source of the shots that killed the driver was not identified.

Marines and Navy Seabee personnel recovered the tank and its crew Sunday. The men's names were being withheld until their families are notified.