A US Marine is dead and 8 service members are missing after an amphibious assault vehicle sank off the coast of California

• One US Marine is dead and eight service members are missing after an accident involving an amphibious assault vehicle off Southern California on Thursday, the I Marine Expeditionary Force tweeted early Friday.
• The AAV sank completely, the assumption being that the heavy tracked vehicle "went all the way to the bottom," Lt. Gen. Osterman, the I MEF commanding general, explained in a press briefing Friday afternoon.
• The accident occurred during a routine training exercise near the island of San Clemente, the US Marine Corps told Business Insider in a statement earlier in the day.
• The Navy and the Coast Guard are leading the search for the missing Marines, the service said.

A US Marine is dead and eight service members, specifically seven Marines and one Navy sailor, are missing after an accident involving an amphibious assault vehicle off the coast of Southern California on Thursday.

"1 Marine has died, 8 service members remain missing and 2 were injured after an AAV mishap July 30 off the coast of Southern California," the I Marine Expeditionary Force tweeted early Friday, adding that all of the Marines in the vehicle were assigned to the 15th Marine Expeditionary Unit.

"Search and rescue efforts are still underway with support from the Navy and Coast Guard," the tweet said.

Fifteen Marines and one Navy sailor were aboard the AAV, which reported that it was taking on water at 5:45 p.m. local time Thursday. The AAV sank completely, the assumption being that the heavy tracked vehicle "went all the way to the bottom," Lt. Gen. Osterman, the I MEF commanding general, said in a press briefing Friday afternoon.

The general said that other units saw the AAV sink.

The deadly incident occurred during a routine training exercise near the island of San Clemente, the US Marine Corps told Business Insider in an emailed statement earlier in the day.

The Corps said that of the injured pair, one was in critical condition and one was in stable condition.

As for the missing, the service said the search and rescue operations involved a number of assets, including four helicopters — three from the Navy and one from the Coast Guard, the warships USS John Finn, USS Somerset and USS San Diego, several small boats from the USS Makin Island, and a Coast Guard vessel. The search for the missing sailor and Marines is still ongoing.

"We are deeply saddened by this tragic incident," said Col. Christopher Bronzi, the commanding officer of the 15th Marine Expeditionary Unit. "I ask that you keep our Marines, Sailors, and their families in your prayers as we continue our search."

Marine Corps Commandant Gen. David Berger said Friday afternoon that he is putting a pause on AAV operations in the water until the cause of the accident can be determined.

"All AAVs across the fleet will be inspected," the Corps' top general further stated, adding that Thursday's accident is under investigation.