(Reuters) - Seven U.S. Marines were killed and seven people injured during a training exercise at a military ammunition storage facility in western Nevada, U.S. military officials said Tuesday.
The explosion occurred Monday at 10 p.m. PDT during a Marine training exercise at the Hawthorne Army Depot in western Nevada, said facility manager Russ Collier.
Victims were airlifted to Renown Regional Medical Center with injuries that included penetration trauma, fractures and vascular injuries, said Stacy Kendall, a spokeswoman for the medical center.

Some news reports indicated that a traffic accident may have preceded the explosion.
The Marines were from Camp Lejeune, North Carolina, a spokeswoman said.
The cause of the explosion remains under investigation, said Marine Lt. Col. Neil Murphy Jr.
Hawthorne Army Depot, about 135 miles south of Reno, is a 147,000-acre site used for the storage and destruction of demilitarized ammunition.
It was first established as a naval staging area for bombs, rockets and ammunition, and was used by the U.S. Navy during most of World War II. The facility was transferred to the Army in 1977.
"We send our prayers and condolences to the families of Marines involved in this tragic incident," said Marine Maj. Gen. Raymond Fox in a statement. "We mourn their loss, and it is with heavy hearts we remember their courage and sacrifice."
The names of the dead and injured will be released following notification of their families.
The accident follows a week after a U.S. military plane assigned to a Washington state Naval Air Station crashed during a routine training flight, killing all three crew members on board.