Search and rescue efforts were still underway Friday night for the seven missing sailors and one sailor, with the support of the Navy and Coast Guard.
At least two others were injured in the crash, which took place on Thursday, and were taken to hospitals in Southern California, according to a statement from the 1st U.S. Marine Corps Expeditionary Force.
One is in critical condition and the other is stable, according to the Marines.
“This tragic incident is deeply saddened and closely monitored. Keep our Marines, sailors and their families in your prayers as the search continues,” Defense Secretary Mark Esper retweeted the tweet.
The incident occurred during a 15th Marine Expeditionary Unit and a routine training exercise by the Amphibious Ready group on Makin Island in the vicinity of San Clemente Island, the Marines reported.
The incident began around 5:45 p.m. local time on Thursday, when sailors from an amphibious assault vehicle reported taking water. Sixteen people were inside the vehicle at the time of the accident. Eight have recovered.
One Marine was killed, two sailors are in critical but stable condition, and another five aboard his ship, U.S. Navy Corps Commander General David Berger said in a press release.
“I have led to an immediate suspension of water operations with assault amphibious vehicles until the causal factors of this mishap are better understood,” Berger said. “The first step is to conduct a search and rescue and take care of their families, that’s why it’s the focus today.”
The amphibious assault vehicle weighs approximately 26 tons and is believed to have sunk to the bottom of the ocean, which is hundreds of feet deep at the site. The AAV is below the depths where divers can go, so the Navy is assisting and providing resources that can go down and take a look at the ship, according to Marine Colonel Jody Osterman.
According to Osterman, the men who were found were wearing normal combat equipment, including armor on their bodies. Includes an inflatable vest. Some of the sailors who were picked up were floating in the ocean.
The search uses a Coast Guard cutter and Navy, Navy and Coast Guard helicopters, along with a destroyer and other surface ships.
“Literally all the assets we had available to search for were launched,” Osterman said.
All service members in the incident are assigned to the 15th MEU based at Pendleton Camp.
The name of the killed navy will be retained until 24 hours after notification of the next relative. The incident is under investigation.
This story has been updated with additional information about the search Friday night.
CNN’s Shawn Nottingham contributed to this report.