A mortar explosion at a U.S. Army munitions depot in Nevada killed seven Marines from Camp Lejeune, North Carolina, and injured eight other service members during a live-fire training exercise, U.S. military officials said on Tuesday.
A Marine Corps official said a 60mm mortar round exploded prematurely on Monday night during training at the Hawthorne Army Depot in western Nevada. The cause was under investigation.
"The Marines were conducting live fire and maneuver training at the Hawthorne Army depot," Brigadier General Jim Lukeman told a news conference in North Carolina. "A mortar round exploded in the mortar tube, causing the deaths of seven. ... We don't know yet what caused this malfunction."
The blast was among the deadliest such training accidents on U.S. soil in recent years. In February 2012, seven Marines were killed when two helicopters collided during an exercise along the California-Arizona border.
The Marines killed on Monday had been undergoing training for the past month at the Marine Corps Mountain Warfare Training Center in Bridgeport, California, and at Hawthorne.
"This is part of the type of training that we do just to maintain a force in readiness," Lukeman said. "It's not specifically linked to a nearby deployment."
The Marines ordered a blanket suspension of the use of 60mm mortars pending a review after the blast, Marine Corps spokeswoman Captain Kendra Motz said in a statement.
The explosion's 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.
Seven Marines and a Navy sailor were wounded. Of those, six were in serious or very serious condition, including the sailor, while a seventh suffered minor injuries and an eighth was treated and released, the Marines said in a statement.
The explosion occurred close to 10 p.m. PDT (0500 GMT Tuesday) during an exercise at the Hawthorne depot, about 92 miles (150 km) southeast of Reno, said facility manager Russ Collier.
The identities of the dead, all from the 2nd Marine Division, and injured had not been made public, but will be released after their families are notified.
U.S. Defense Secretary Chuck Hagel was receiving updates on the accident, Pentagon spokesman George Little said, adding 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.
Hawthorne Army Depot is a 147,000-acre (60,000-acre) site used for the storage and destruction of demilitarized ammunition. Its 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 website.
The facility was established as a naval staging area for bombs, rockets and ammunition, and was used by the Navy during most of World War Two. It was transferred to the Army in 1977.
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.