By Cynthia Johnston
LAS VEGAS (Reuters) - An explosion at a U.S. Army munitions depot in the western Nevada desert killed seven Marines from Camp Lejeune, North Carolina, and injured seven more during a training exercise, U.S. military officials said on Tuesday.
Army and Marine officials said the cause of the Monday night blast was under investigation, but a military official who spoke on condition of anonymity said initial reports from the scene indicated that a 60mm mortar round exploded prematurely in the tube of a mortar launcher.
The official said three Marines were killed instantly.
Victims were airlifted to Renown Regional Medical Center in Reno with injuries that included penetration trauma, fractures and vascular injuries, said Stacy Kendall, a spokeswoman for the medical center. The status of the injured was unclear.
The explosion occurred at 10 p.m. PDT (5 a.m. GMT Tuesday) during a Marine training exercise at the Hawthorne Army Depot, about 92 miles (152 km) southeast of Reno, said facility manager Russ Collier.
U.S. Defense Secretary Chuck Hagel was receiving updates on the accident, Pentagon spokesman George Little said, adding that the incident struck a nerve with Hagel, himself an infantry veteran of the Vietnam war.
"This brought back memories of a training accident when he was in the U.S. Army when two soldiers were killed in a training accident, so he takes these incidents very much to heart," Little said.
Other politicians expressing condolences in the aftermath of the accident included Nevada Governor Brian Sandoval and U.S. Senate Majority Leader Harry Reid of Nevada.
Hawthorne Army Depot is a 147,000-acre site used for the storage and destruction of demilitarized ammunition. The facility's location in Nevada's isolated high desert is also considered an ideal training environment for Special Operations forces preparing for deployments to Southwest Asia, according to a U.S. military web site.
The facility 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 Two. It was transferred to the Army in 1977.
The names of the dead and injured will be released following the notification of their families.
The accident came 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.
(Reporting by Chris Francescani in New York, David Alexander in Washington D.C. and Cynthia Johnston in Las Vegas; Writing by Chris Francescani and Steve Gorman; Editing by Paul Thomasch, Nick Zieminski, Leslie Gevirtz)