Six U.S. Marines were critically wounded and nine others injured in a fiery training accident involving an Amphibious Assault Vehicle (AAV) on Marine Corps Base Camp Pendleton, according to the Marine Corps.

The land-based training accident happened at approximately 9:33 a.m. Wednesday, 1st Marine Division public affairs officer 1st Lt. Paul Gainey said. Camp Pendleton is a U.S. Marine Corps base located north of San Diego; the base had more than 42,000 active duty personnel.

At the time of the incident, the Marines were conducting a scheduled Combat Readiness Evaluation, a standard training for infantry battallion, Gainey said.

The AAV had an accident and caught on fire, a Pendleton spokesman said. The vehicle is used to transport Marines from sea to land and has been used since the 1970s.

The incident injured 15 Marines from 1st Battalion, 1st Marine Regiment and 3rd Assault Amphibian Battalion.

Eight Marines were medically evacuated to the UC San Diego Health's Burn Center. Of those eight Marines, three are in critical condition and five are in serious condition.

Four other Marines were taken to the University of California Irvine Medical Center. Three of those Marines are in critical condition and one is in serious condition.

One Marine was taken to Scripps Memorial Hospital La Jolla and is in stable condition.

Two Marines were taken to Naval Hospital Camp Pendleton with minor injuries.

"Our thoughts and prayers are with the Marines and their families as they receive medical care," Gainey said in the statement.

The incident is just the latest in a string of accidents at the base, some fatal.

Earlier this month, U.S. Marine Corps officials announced that another Marine had died during training at the base north of San Diego County. On Aug. 30, Private First Class Michael P. Giannattasio was found unresponsive during a land navigation training event with the Basic Reconnaissance Course, School of Infantry West, aboard Camp Pendleton. When medics arrived, they tried to resuscitate the Marine, but it was too late. He was pronounced dead at the scene.

In 2015, a Marine was discovered dead at a shooting range on the base; he was participating in a training exercise in which live ammunition was used.

Several years ago, in Nov. 2013, four U.S. Marines were killed during a range maintenance operation.

Wednesday's accident remains under investigation.

No other information was available.

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