The explosion late Monday in western Nevada killed seven Marines immediately. An eighth man died Tuesday of his injuries, the Reno Gazette-Journal reported.
The Marines were based at Camp Lejeune in North Carolina but were on a training exercise at Hawthorne Army Depot in the high desert in western Nevada. The Marines were withholding the names of the dead pending notification of their families, CNN said.
"Let me say to the families of our Marines and sailors that our hearts go out to you," Brig. Gen. James Lukeman, commander of the 2nd Marine Division, said in a statement. "We appreciate your sacrifice, and we'll do all that we can to continue to support you."
Mark Earnest, a spokesman for Renown Regional Medical Center in Reno, said four of the survivors were in serious condition, two in fair condition and one had been released from the hospital. One of the injured was a sailor.
The Marines said no 60 mm mortar rounds and launching tubes will be used until the accident has been investigated, CNN reported.
Dr. Michael Morkin, a trauma surgeon at the medical center, said the injured, all men under the age of 30, suffered "blunt force injuries." He said they resembled the injuries staffers at Renown saw in 2011 when a plane crashed during an air race, killing the pilot and 11 spectators, the Gazette-Journal said.