Seven marines died and seven more were injured in an explosion during a training exercise at an army facility in Nevada late Monday.
Details remain sketchy early in the investigation.
The explosion occurred at the Hawthorne Army Depot, an ammunition storage facility.
The depot sits on just under 150,000 acres of land near Reno, Nevada.
It claims to be the "world's largest depot," and stores ammunition and explosives that would be used by the U.S. military after the first 30 days of a major conflict.
The depot was slated to be closed about 8 years ago under the military's base realignment and closure program, but the Pentagon changed its mind because the facility also provided a pre-deployment training ground for the Marines.
The units involved in Monday's explosion and the names of the marines have not been released.