Six Marines were critically injured in Thursday’s vehicle rollover accident at Camp Pendleton that left one Marine dead.

The Marines were in a 7-ton truck that flipped over on a paved two-lane road on the California base. The Marines were returning from a training exercise at the time of the crash.

The crash killed a Marine and and injured 18 others, the Marine Corps said Thursday without detailing the extent of the injuries.

On Friday, the Marine Corps issued an update that said the injured were being treated at five hospitals in the San Diego area.

The statement said in addition to the critically injured Marines, eight were in stable condition and four were treated and released.

The Marine who was killed was from the 1st Marine Division. First Lt. Colleen McFadden said that person’s name would be released after relatives were notified.

Some of the injured went to Palomar Medical Center in Escondido, hospital spokeswoman Bobette Brown said without providing other details.

"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 Marines were in a workhorse troop carrier for the Navy and Marine Corps called a Medium Tactical Vehicle Replacement or MTVR, according to the Associated Press. The vehicle is built to operate on any terrain and in extreme heat and cold weather.

Camp Pendleton, a vast seaside base north of San Diego, 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.

The Associated Press contributed to this report.