Baghdad, Iraq ? Four U.S. Marines died in Iraq when their tank rolled off a bridge into a canal and they drowned, the military said today.

The U.S. command said the deaths were not caused by hostile action.

The accident happened Thursday when the four Marines with Regimental Combat Team 5 were traveling in a tank near Karmah, 50 miles west of Baghdad in Anbar Province. Many Sunni-led insurgent groups are based in the area.

The names of the deceased were being withheld pending notification of their relatives.