(CNN) — Four Marines were killed Wednesday during a range maintenance operation at Camp Pendleton in California, the military said.
The incident was the deadliest for Pendleton since seven Marines were killed in a February 2012 midair collision between helicopters along the Arizona-California border, said a military spokesman. Six of them were based at Camp Pendleton, California, and the other was from Yuma, Arizona.
Their names of the four Marines killed this week weren\’t immediately released because their families were still being notified, the Marines said.
The four Marines were working in a range area used for live-fire exercises, but the deaths didn\’t occur under such live fire, said a military spokesman who asked not to be identified while the matter is under investigation.