A search and recovery operation is underway after a U.S. Marine, who was serving aboard the USS Anchorage during a training, was reported missing early Thursday, off the coast of Southern California, according to a press release from the U.S. Navy.

A search and rescue operation was first initiated at 1:21 a.m. on Thursday by The Makin Island Amphibious Readiness Group. This involved a response from the U.S. Navy, U.S. Marine Corps, U.S. Coast Guard, and U.S. Air Force, which “spanned approximately 2,400 square miles over the course of 43 hours using three surface ships and 12 aircraft,” the Navy’s Deputy Public Affairs Officer said.

“The Marine was serving abroad amphibious transport dock ship USS Anchorage (LPD-23) during integrated training between the 13th Marine Expeditionary Unit (MEU) and Makin Island Amphibious Ready Group,” they said.

The USS Anchorage (LPD-23) is homeported in San Diego. The 13th MEU is also based at Marine Corps Base Camp Pendleton.

The operation then transitioned to a search and recovery mission as of 9:00 p.m. Friday, the Navy said.

“Our thoughts and prayers are with the family and all who are affected during this difficult time.”

They said in accordance with U.S. Navy policy, the Marine’s name will be withheld until after 24 hours have passed from the next-of-kin notification.