The type of shell that exploded on Wednesday morning at theZulu Impact Area and how exactly it was detonated remain underinvestigation, the spokesman, Jeff Nyhart said.
The range, located deep in the interior of the sprawlingbase, is used as a target zone for artillery and aerial bombingpractice, and requires routine maintenance to keep it clear ofobstructions and unexploded rounds.
The four dead Marines were ordnance disposal techniciansbased at Camp Pendleton, not new recruits, and "were handlingunexploded ordnance" when the blast occurred, Nyhart said.