LOS ANGELES (AP) — With the possibility of finding survivors all but gone and the ocean search shifted from a rescue effort to a recovery mission, focus fell Monday on what caused a Marine Corps helicopter and U.S. Coast Guard plane to collide over the Pacific.

Petty Officer First Class Allison Conroy said there was little chance of finding survivors among the seven military personnel aboard the Coast Guard C-130 and the two in the Marine Corps AH-1W Super Cobra helicopter.

“We always hold out some hope, but at this point the Coast Guard has suspended the active search for survivors,” Conroy said Sunday.

The two aircraft collided Thursday evening as the Coast Guard was searching for a missing boater. The Marine helicopter was flying in formation with another Cobra helicopter and two transports on a nighttime training exercise.

The crash investigation was being conducted jointly by the Coast Guard and the Marine Corps with support from the Federal Aviation Administration and the National Transportation Safety Board, Petty Officer Henry Dunphy said Sunday.

The accident happened in airspace uncontrolled by the FAA and inside a so-called military warning area, which is at times open to civilian aircraft and at times closed for military use, FAA spokesman Ian Gregor said. He did not know the status of the airspace at the time of the crash.

Minutes before the collision, the FAA told the C-130 pilot to begin communicating with military controllers at Naval Air Station North Island in San Diego Bay, but it was not known if the pilot did so, Gregor said.

A top Coast Guard official said Saturday he believed the C-130 pilot had spoken with the military controllers before the accident.

Accident investigators would review communications between the pilots and between the pilots and the FAA and military controllers, said Capt. Tom Farris, commander of the Coast Guard’s 11th District.

Investigators are also collecting witness statements from those aboard the three other Marine aircraft and will check to see if any distress calls were made.

Kenneth Claiborne said Sunday that his son Marine 1st Lt. Thomas Claiborne, who was on the helicopter, had been declared deceased. He declined to comment further and referred calls to a Marine spokesperson.

The mother of Lt. Adam W. Bryant, 28, of Crewe, Va., who was a co-pilot on the Coast Guard plane, said she hadn’t given up hope despite the Coast Guard’s announcement.

“Miracles do happen,” Nina Bryant said Sunday. “Miracles every day.”

Nine aircraft searched over a 644-square-mile patch of ocean in waters about 2,000 feet deep. Debris from both aircraft was found, but there was no sign of the crew members.

All seven aboard the Coast Guard plane are stationed at the Coast Guard Air Station in Sacramento, Calif. Among the other missing crew members on the plane were Lt. Cmdr. Che Barnes, 35, of Capay, Calif.; Chief Petty Officer John F. Seidman, 43, of Carmichael, Calif.; Petty Officer 2nd Class Carl P. Grigonis, 35, of Mayfield Heights, Ohio; Petty Officer 2nd Class Monica L. Beacham, 29, of Decaturville, Tenn.; Petty Officer 2nd Class Jason S. Moletzsky, 26, of Norristown, Pa., and Petty Officer 3rd Class Danny R. Kreder II, 22, of Elm Mott, Texas.