Seven US Marines have been killed and several others injured after a mortar shell exploded unexpectedly during a training accident the Hawthorne Army Depot in Nevada.
A Marine Corps official said the blast occurred on Monday night.
At least eight men are in hospital, three in a serious condition and five in a stable condition.
It is not clear if the mortar exploded prematurely in its firing tube or if more than a single round exploded.
The US Marines Corps has banned use of 60 mm mortars, which normally need three to four troops to operate, until an investigation can establish what caused the incident.
Those caught in the Monday blast at 22:00 local time were members of the 2nd Marine Division.
Renown Regional Medical Center in Reno said it had received nine patients, one of whom died.All the patients were men under the age of 30, who suffered penetrating trauma, fracture and vascular injuries, said Stacy Kendall, a spokeswoman for the facility.
Marine commander Maj. Gen Raymond Fox said in a news release: “We send our prayers and condolences to the families of Marines involved in this tragic incident.
“We remain focused on ensuring that they are supported through this difficult time.
“We mourn their loss, and it is with heavy hearts we remember their courage and sacrifice.”