Marines killed at  Camp Pendleton

Vehicles file through the main gate of Camp Pendleton Marine Base. Four Marines were killed in an accident on the base. (Lenny Ignelzi / Associated Press / November 13, 2013)

The four Marines killed while clearing an artillery range of unexploded ordnance at Camp Pendleton were members of an elite explosive ordnance disposal team, all with combat experience.

"Our thoughts and prayers are with the families of the Marines we lost yesterday," said Brig. Gen. John W. Bullard, the base commanding general. "Explosive ordnance disposal is a small and tight-knit community, not just in the Marine Corps but in the entire U.S. military."

Cause of the Wednesday accident on the Zulu artillery range is under investigation. There was no live-fire training at the range when the accident occurred, officials said. Clearing the range of ordnance is a routine part of maintenance.

The Zulu area is used for firing explosive munitions such as grenades, mortars, artillery and rockets and for dropping munitions from aircraft. The area where the four Marines were working had not been swept for unexploded ordnance in five years, the Marines said.

Killed were:

Staff Sgt. Mathew Marsh, 28, of Long Beach. Marsh joined the Marine Corps in 2003. He had deployed twice to Iraq and twice to Afghanistan.

Gunnery Sgt. Gregory Mullins, 31, of Bayou L'Ourse, La. He joined the Marine Corps in 2002 and had deployed twice to Afghanistan.

Sgt. Miguel Ortiz, 27, of Vista, Calif. He joined the Marine Corps in 2006 and had deployed to Iraq and Afghanistan.

Staff Sgt. Eric Summers, 32, of Poplar Bluff, Mo. He joined the Marine Corps in 2000 and had deployed to Iraq and three times to Afghanistan.

All four had deployed to Afghanistan as recently as last year. Each had received a Combat Action Ribbon, awarded to Marines who come under enemy fire and return fire.

Explosive ordnance disposal has been one of the most crucial and dangerous missions in Iraq and Afghanistan, where buried bombs have been used as a "weapon of choice" against U.S. and coalition troops.

Two other Marines and a Navy corpsman were injured in the accident and were treated and released after receiving medical assistance at the scene, the Marines said.

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tony.perry@latimes.com