Seven U.S. Marines and one Sailor are presumed dead after going missing during a training "mishap" off the Southern California coast on Thursday, officials announced in a press release late Saturday night.
The 15th Marine Expeditionary Unit, I Marine Expeditionary Force, and the Makin Island Amphibious Ready Group concluded their search and rescue operation after an extensive 40-hour search for the service members, the release stated.
“It is with a heavy heart, that I decided to conclude the search and rescue effort,” Col. Christopher Bronzi, 15th MEU Commanding Officer, said in a statement. “The steadfast dedication of the Marines, Sailors, and Coast Guardsmen to the persistent rescue effort was tremendous.”
Officials determined that there was little probability of a successful rescue given the circumstances of the incident, according to the release.
In addition to the eight service members now presumed dead, a ninth U.S. Marine died during the training mishap and another was in critical condition.
The deceased Marines and Sailor were not immediately identified.
Fifteen Marines and one sailor were inside an amphibious assault vehicle near San Clemente Island on Thursday when they reported taking on water at about 5:45 p.m., according to officials.
Gen. David Berger said at a news conference Friday afternoon, "The vehicle sank after taking on water."
Two amphibious assault vehicles and a safety boat were nearby. Some of the rescued Marines were found bobbing in the water after successfully deploying floatation devices, which all on board had been equipped with, said Lt. Gen. Joseph L. Osterman.
The 26-ton vehicle appeared to sink in "several hundred feet of water" more than 1,000 meters from the northwest corner of the island, officials said.
“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,” Bronzi said on Twitter.
The incident is still under investigation, officials said.
This article first appeared on NBC News.