The Marine Corps says seven Marines have been killed in a training accident at the Hawthorne Army Depot, Nev.
The Corps said in a statement Tuesday that the accident at around 10 p.m. Monday also injured several with the 2nd Marine Division.
A Marine Corps official now says the deadly accident was caused by the explosion of a 60mm mortar, which exploded unexpectedly during a training accident.
The Marines immediately issued an indefinite moratorium on firing of all such mortars worldwide until an investigation clears as safe the type of weapon and ammunition in the tragedy.
The official, speaking on condition of anonymity, said it was not immediately clear whether the mortar exploded prematurely inside its firing tube or whether more than a single round exploded. The official was not authorized to speak to a reporter about the accident.
The 60mm mortar is a weapon that traditionally requires three to four Marines to operate, but it's common during training for others to observe nearby.
The injured were taken to area hospitals for treatment and further evaluation.
The identities of those killed were not released pending notification of their families.
The Hawthorne Army Depot stores and disposes of ammunition. The facility is made up of hundreds of buildings spread over more than 230 square miles.