By Dan Whitcomb
LOS ANGELES, March 6 (Reuters) - Two U.S. Marines have been relieved of their commands over an explosion at the Camp Pendleton base that killed four bomb specialists in November, probably when a live grenade fell into a demolition pit, military officials said on Thursday.
A Marine investigation could not establish the exact cause of the blast, in part because the people who likely directly witnessed the incident were killed by the ensuing explosion, said a public affairs officer at the Southern California base.
According to the Marines, four explosive ordnance disposal specialists were killed at Camp Pendleton, north of San Diego, when a grenade was likely "dropped, kicked or bumped" into a demolition pit they were working in.
"Many of the training evolutions we conduct are inherently dangerous, especially when dealing with explosives and munitions," Brigadier General John Bullard, commander of the base, said in a statement announcing the findings.
"We are deeply saddened by the tragic loss of four Marines during a training evolution; their loss is felt throughout the Marine Corps," Bullard said.
Bullard relieved the two Marines in charge of the base explosive ordnance disposal, or EOD, section for "loss of trust and confidence in their ability to ensure proper preparation for and conduct of EOD proficiency training and lack of adherence to the established norms," the base said.
The base statement did not identify the two Marines.
Bullard also ordered an immediate review and revision of policies and procedures for explosive ordnance disposal training aboard all Marine Corps ranges in the U.S. West, according to the base.
The Los Angeles Times, which obtained a copy of the full report, said that Marines who died had been assigned to clear ordnance from an impact range on the base and that the grenade set off several dozen rounds that had been gathered for demolition.
The range, located deep in the interior of the sprawling base, is used as a target zone for artillery and aerial bombing practice, and requires routine maintenance to keep it clear of obstructions and unexploded rounds.
The four Marines killed in the accident have previously been identified as Staff Sergeant Mathew Marsh, 28, of Long Beach, California; Gunnery Sergeant Gregory Mullins, 31, of Bayou L'Ourse, Louisiana; Sergeant Miguel Ortiz, 27, of Vista, California; and Staff Sergeant Eric Summers, 32, of Poplar Bluff, Missouri.
Camp Pendleton, 40 miles (65 km) north of San Diego, is the main West Coast base for the Marine Corps. The base is home to 37,000 active duty Marines and sailors. (Editing by Cynthia Johnston and Mohammad Zargham)