by Jim Michaels, Tom Vanden Brook and Doug Stanglin, USA TODAY
Seven Marines were killed and seven wounded late Monday during a training exercise at Hawthorne Army Depot in Nevada, according to a military and defense officials.
The 230-square-mile facility, located about 140 miles southeast of Reno, stores ammunition that is awaiting demilitarization, but is also used for desert training.
The Marines were part of the 2nd Marine Division, a ground combat force based at Camp Lejeune, N.C.
A senior defense official said it appears that a mortar round exploded inside a firing tube instead of flying out. The official, speaking on background, cautioned that initial reports could change on the cause.
"We send our prayers and condolences to the families of Marines involved in this tragic incident. We remain focused on ensuring that they are supported through this difficult time," said Maj. Gen. Raymond C. Fox, commanding general of the 2nd Marine Expeditionary Force. "We mourn their loss, and it is with heavy hearts we remember their courage and sacrifice."
An official at the depot tells KRNV that the explosion was an accident unrelated to the ammunition stored at the depot. The incident occurred just before 10 p.m. local time.
The U.S. Joint Munitions Command says on its website that the depot is an "archive site" for storing slow-moving ammunition and stocks awaiting demilitarization. It says the the depot also provides "high desert training facilities" for military units.
NBC reports that the facilities is used for training Special Operations forces preparing for deployment to the Middle East.
Contributing: Associated Press