The Marines were on a range maintenance operation at the base’s Zulu impact area when the accident occurred at around 11 a.m. PST, base spokesman Lt. Ryan Finnegan said.
“The cause of the accident is under investigation,” Finnegan said.
A NBC report said the deaths were due to detonation unexploded ordnance.
The Zulu impact area is where ordinance from artillery, mortars and fighters strike during training.
The names of the victims will likely be released on Friday, Finnegan said.
It’s unclear the type of maintenance the Marines were performing. Range maintenance includes cutting grass, animal control as well as removal of unexploded ordnance.