( CNN ) -- Authorities have decided to call off a search-and-rescue mission for nine people who may have plunged into the Pacific Ocean off southern California after a Coast Guard C-130 plane and a Marine AH-1 Cobra helicopter collided Thursday night . `` I 've reached the conclusion that hope is no longer viable , '' Coast Guard Rear Adm. Joseph Castillo said Sunday . `` We no longer believe there is any chance somebody could still be alive . '' California Gov . Arnold Schwarzenegger offered his condolences to family members of the missing Sunday . `` Together , we send our thoughts and prayers to their families and friends , '' Schwarzenegger said in a statement . `` Our hearts are with them during this difficult time . '' Searchers had scoured the ocean for 60 hours without finding any sign of survivors . They reported Saturday that the search had covered 644 square miles . The Navy , Marine Corps and Customs Border Protection helped in the search . The Coast Guard weighed the exhaustive nature of the search , the wreckage , the nature of the collision , the temperature of the water and the time elapsed . A Coast Guard captain said Friday that survivability could be up to 20 hours . On Saturday night , relatives of the missing were briefed about the decision to call off the rescue effort . The order was to go into effect as soon as the planes involved in Sunday morning 's dawn search returned about 9 a.m. Coast Guard pilots had been searching for a missing person in the water . That person was `` reported to have gotten in a dinghy and attempted to row to Catalina [ Island ] , '' Coast Guard Capt . Thomas Farris said Friday . `` We were searching in that area because of the drift that would have naturally occurred after that event . '' The collision occurred about 7 p.m. Thursday , when the Coast Guard plane with a seven-person crew collided with a Marine AH-1 Cobra helicopter carrying two people . A pilot not involved in the incident reported seeing a fireball about 7:10 p.m. Thursday near the crash site . The two Marine pilots were conducting routine training about 15 miles off San Clemente Island when their helicopter collided with the U.S. Coast Guard plane . Marine Corps Air Station Miramar identified them as Maj. Samuel Leigh and 1st Lt. Thomas Claiborne , both with Marine Light Attack Helicopter Squadron 469 . The Coast Guard 's seven missing personnel were stationed at Coast Guard Air Station Sacramento , California , where their aircraft was based . Castillo has said that an investigation was beginning with the Marine Corps . A large debris field has been located , and pieces have been collected , the Coast Guard spokesman said . The Coast Guard identified its seven missing personnel as Lt. Cmdr . Che J. Barnes of Capay , California , aircraft commander ; Lt. Adam W. Bryant of Crewe , Virginia , co-pilot ; Chief Petty Officer John F. Seidman of Stockton , California , flight engineer ; Petty Officer 2nd Class Carl P. Grigonis of Mayfield Heights , Ohio , navigator ; Petty Officer 2nd Class Monica L. Beacham of Decaturville , Tennessee , radio operator ; Petty Officer 2nd Class Jason S. Moletzsky of Norristown , Pennsylvania , air crew ; and Petty Officer 3rd Class Danny R. Kreder II of Elm Mott , Texas , drop master . The Coast Guard announced that a memorial service for personnel missing in the collision will be at 11 a.m. PT Friday at the Coast Guard station in Sacramento .
Spokesman : Search halted because ` ` boat is no longer viable '' Coast Guard plane and Marine Corps helicopter collided Thursday . Coast Guard craft had been on search for missing boater .