By Marty Graham
SAN DIEGO (Reuters) - Four U.S. Marines were killed on Wednesday in an accident while clearing a training area used as an artillery and aerial bombing range at Camp Pendleton in Southern California, a military spokesman said.
NBC News reported the Marines were killed when unexploded ordnance unexpectedly detonated, but the spokesman could not immediately confirm that, saying only the Marines had been clearing the area.
Marines spokesman Lieutenant Ryan Finnegan said the clearance operation would have involved anything necessary to keep the range free of obstructions, which could include disposing of ordnance. But he could not say they were handling ordnance when the accident occurred.
The cause of the accident, which happened on Wednesday morning at the Zulu Impact Area in the interior part of the base, was under investigation.
No live-fire exercise was under way at Zulu at the time, and while such an exercise was occurring at neighboring Whiskey Impact Area, it played no role in the deaths, Finnegan said.
"We offer our heartfelt prayers and condolences to the families of the Marines lost today in this tragic accident," Brigadier General John Bullard, commanding general of the base, said in a statement. "Our first priority is to provide the families with the support they need during this difficult time."
Finnegan said the Marines killed were not new recruits and were based at Camp Pendleton, but the military did not release their ages or other details about them.
Training at Camp Pendleton, including the live fire at Whiskey Impact Area, continued after the fatalities, he said.
The Zulu Impact Area is a restricted zone because of the danger of unexploded ordnance, according to Camp Pendleton's website. As a result, efforts to contain wildfires and study biology there are limited, the website description stated.
Seven Marines were killed in an accidental munitions depot blast in Nevada in March. In May, a U.S. Navy SEAL was killed in a vehicle accident during a training exercise at Fort Knox in Kentucky.
In September 2011, two Marines aboard a helicopter died when it crashed during a training mission at Camp Pendleton, two months after a Marine was killed when another helicopter went down at the base.
Camp Pendleton, 40 miles north of San Diego, is the main West Coast base for the Marine Corps.
(Reporting by Marty Graham in San Diego; Writing by Alex Dobuzinskis; Editing by Cynthia Johnston and Peter Cooney)