Officials say it was a Marine Corps training exercise accident, and involved servicemen from the 2nd Marine Division.
"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," said Maj. Gen. Raymond C. Fox, II MEF commanding general, in a statement to the press. "We mourn their loss, and it is with heavy hearts we remember their courage and sacrifice."
The cause of the incident is under investigation.
Russ Collier told KRNV-TV in Reno that the explosion Monday night was an accident unrelated to the ammunition that is stored at the military facility near the small desert community of Hawthorne, about 140 miles southeast of Reno.
The Mineral County sheriff's office says it does not have any details.
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.
The Marine Corps said it is withholding the identities of those killed until next of kin notification. The status of those injured has not been provided yet.