Seven U.S. Marines were killed and at least seven others were wounded after a Monday night explosion at the Hawthorne Army Depot, roughly 100 miles south of Reno, Nev.
It's not clear what caused the explosion. According to NBC News, initial reports say that the Marines were either loading a 20-millimeter mortar shell into a tube during a training exercise, or were lifting the shell as they prepared to fire it. The military is investigating to determine what happened.
"We mourn their loss, and it is with heavy hearts we remember their courage and sacrifice," said Marine Corps Maj. Gen. Raymond C. Fox in a statement.
The website of the depot says that it specializes in "disposing of ordinance." The 147,236-acre site in the "high desert" also prepares troops for deployments overseas, the website says, and features "igloos, supply warehouses, maintenance buildings, munitions sheds, and office buildings."
The victims of the explosion were from the 2nd Marine Division, which is based at Camp Lejeune, N.C. Their identities have not been made public, pending notification of their families.