Seven Marines were killed in an explosion Monday night during a Marine Corps training exercise at Hawthorne Army Depot in western Nevada, the Marine Corps said Tuesday. Seven others were injured.
The cause of the blast was a 60 mm round that detonated inside a mortar tube, Brig. Gen. James W. Lukeman, the commanding general of the 2nd Marines, told reporters Tuesday.
Two Marines and one sailor are in very serious condition, and three Marines are in serious condition, Lukeman said. Another Marine suffered minor wounds.
"Let me say to the families of our Marines and sailors that our hearts go out to you," said the general, whose division is based at Camp Lejeune in North Carolina. "We appreciate your sacrifice, and we'll do all that we can to continue to support you."
The Marines will release the names of the deceased 24 hours after their relatives have been notified.
Lukeman wouldn't give any details about which Marine unit was involved but said they were involved into a mountain training exercise that involved live ammunition. They had been training at Hawthorne and the nearby Marine mountain warfare training center in Bridgeport, California, for about a month.
Mortar rounds from the same lot as the shell that detonated will be pulled from use, he said.
A Marines spokeswoman said all other 60 mm mortar rounds will continue to be used in training and in Afghanistan.
"There is some talk of a stop-usage on the mortar tubes that are the same ones that were being used at Hawthorne, but that has not taken effect yet," Capt. Kendra N. Motz said.
Senate Majority Leader Harry Reid, who represents Nevada, called it "quite a big explosion" and said the area of the blast was cordoned off as details emerged.
"We don't know exactly what happened, but it was a violent explosion, we know that," he said. "Our thoughts are with those who were injured and, of course, the families of those who lost loved ones."
The Hawthorne Army Depot, about 140 miles southeast of Reno, is used for storing ammunition and weapon stocks awaiting demilitarization. The facility also provides high desert training facilities for military units.
President Barack Obama was immediately made aware of the incident, and the White House is monitoring the situation, spokesman Jay Carney said.
"We are obviously in the early stages of assessing the incident," he said. "It is a tragedy, clearly."
-- CNN's Mike Mount and Tina Burnside contributed to this report.
™ & © 2013 Cable News Network, Inc., a Time Warner Company. All rights reserved.