Many Marines injured in deadly crash in critical condition

SAN DIEGO -- Six of 18 Marines injured in a rollover accident were listed in critical condition Friday, a day after the 7-ton truck carrying them flipped during routine training at Camp Pendleton, killing one Marine.

Eight of the troops were in stable condition and four were treated and discharged from medical facilities in San Diego County, according to the Marine Corps. The Marine who was killed was from the 1st Marine Division, and that person's name will not be released until 24 hours after relatives are notified, officials said.

It's unclear whether the truck - commonly used to transport Marines and haul supplies - hit something, had a mechanical failure or was traveling at a high rate of speed late Thursday afternoon on the vast coastal base dotted with mountains. Authorities said the investigation into the cause of the accident could take months.

"After this tragic training accident, our first concern is for the welfare of our deceased Marine, the injured and their families," Maj. General Daniel J. O'Donohue, commanding general of 1st Marine Division, said in a statement Friday. "They are held close in our hearts and prayers. Our commanders, chaplains, medical personnel and families and surrounding communities have come together in support. We deeply appreciate all the support and sympathy that we have received for this tragic loss."

The truck the Marines were traveling in is considered to be a workhorse for the Navy and Marine Corps, carrying troops, supplies, and heavy equipment. Called a Medium Tactical Vehicle Replacement or MTVR, it is built to go over any terrain and operate in weather conditions ranging from minus-50 degrees Fahrenheit to 125 degrees Fahrenheit. Despite its top heavy appearance, the hulking vehicle can ford 5 feet of water, climb a 60-percent gradient and navigate a 30-degree side slope, according to its manufacturer, Wisconsin-based Oshkosh Corp.

Officials have released few details about the training, including saying whether the truck was on pavement or traveling off-road at the time of the rollover. The Marine Corps said it had no further information to release at this time.

Camp Pendleton is the major West Coast outpost for the U.S. Marine Corps.

In November 2013, four Marines were killed there while clearing explosives in a Camp Pendleton training area.