(KGTV) -- A Marine with a Camp Pendleton-based unit died and a search is underway for eight others from that group following a training accident off the coast of San Clemente Island, U.S. Marine officials said.
Officials said the incident happened around 5:45 p.m. Thursday during a routine training exercise involving the 15th Marine Expeditionary Unit, I Marine Expeditionary Force, and Makin Island Amphibious Ready Group, according to officials.
An amphibious assault vehicle with 15 Marines and one sailor inside reported taking water during the exercise, officials said.
Seven members of the group were rescued and taken to the hospital, but officials confirmed another -- a Marine -- died at Scripps La Jolla Hospital. Two individuals, both Marines, were in critical and stable conditions, respectively.
The five other members have returned to their assigned ship.
The eight members — seven Marines and one sailor — remained missing as of Friday afternoon and were being searched for by the Navy's USS John Finn, three Navy helicopters, several smaller Navy vessels and a U.S. Coast Guard ship and helicopter, Marine officials said.
Officials say that all families of the Marines and the sailor involved have been notified.
"We have not moved into a recovery operation," Gen. David Berger, USMC commandant, told reporters during a mid-afternoon briefing at Camp Pendleton, the home base of the personnel involved the accident.
Friday, officials said that they have covered more than 200 square nautical miles in the search efforts.
An immediate cancelation of AAV use was also ordered at the base and all vehicles will be inspected after the tragedy.
Retired Lieutenant Colonel Hal Kempfer said these vehicles date back to World War II and historically can have issues.
"Even when they go through all the checklist, they can have mechanical problems in the water that they didn’t anticipate," said Kempfer.
He also said that with only half getting out, it's likely that the vehicle took on water very quickly.
"One of the problems is if they take water, the Marines in the back of the vehicle are in a sealed compartment, so whereas the crew can get out fairly quickly, it's tough to get all the Marines out," he said.
Kempfer added that while the goal is to keep everyone safe, even training comes with risks.
"We train like we fight, and we take all the precautions we possibly can but it’s a dangerous business and sometimes training accidents happen," he said, adding that whether a Marine died in combat or in a training drill, they should still be honored and remembered the same way.
A Tweet from the First MEF reads “We are deeply saddened by this tragic incident. I ask that you keep our Marines, Sailors, and their families in your prayers as we continue our search,” said Col. Christopher Bronzi, 15th MEU Commanding Officer.
The name of the Marine who died will not be disclosed until 24 hours after family was notified.