LOS ANGELES, California — The US Marines on Sunday called off the search for seven missing Marines and one Navy sailor who went missing after a vessel sank off the California coast on Thursday night. All eight are presumed dead.

The service members were on an amphibious assault vehicle (AAV) that sank during the exercise. The AAV was carrying 15 Marines and one sailor when it was transferring the sailors from the shores of San Clemente Island near San Diego to a Navy ship when it began to sink.

Eight other Marines were rescued after the accident but one later died. Two others are in a critical condition.

The Marines were attached to the 15th Marine Expeditionary Unit, based at Camp Pendleton.

"It is with a heavy heart that I decided to conclude the search and rescue effort," said Col Christopher Bronzi, commander of the 15th Marine Expeditionary Unit (MEU).

“The steadfast dedication of the Marines, Sailors, and Coast Guardsmen to the persistent rescue effort was tremendous.”

A search operation involved helicopters and ships over an area of more than 1,000 square nautical miles (3,439 sq km), the Marines said in a statement.

The AAV had been returning to the amphibious warship USS Somerset after operating on San Clemente Island when it began to take on water and sank, military officials, said on Friday.

Marines often practice beach assaults in the area.

Col. Bronzi said the effort would now shift to one aimed at finding the bodies of the missing.

The 15th MEU, based at Camp Pendleton, near San Diego, has about 2,200 personnel and conducts rapid-response, conventional amphibious and other maritime operations. — Agencies