Rescuers battled winds of up to 23 mph and waves up to 30 feet Saturday as they searched for 12 Marines who were missing after two helicopters crashed off the Hawaiian island of Oahu.
The winds and waves complicated the search. Authorities at first spotted a debris field that spanned almost seven miles off the coast and set up a safety zone in the area, but the search was later expanded Saturday.
The Coast Guard was notified late Thursday of the crash by a civilian who saw the aircraft flying, then disappear, and a fireball followed. Someone else reported a flare in the sky, Coast Guard spokesman Lieutenant Scott Carr said. It was not clear whether the fireball and the flare were the same.
The Marines were alerted when the CH-53E helicopters carrying six crew members each failed to return to the base at Kaneohe Bay following a nighttime training mission. Hours later, a Coast Guard helicopter and C-130 airplane spotted debris 2½ miles off Oahu.
The aircraft did not issue any distress calls.
A Navy P-3 airplane was scouring the ocean, along with helicopters from the Coast Guard, Army, Navy and Honolulu police and fire departments. Two Navy warships and two Coast Guard cutters were on the scene. Honolulu lifeguards on personal watercraft also were looking.
The Coast Guard was keeping people out of a wide zone that spanned about 30 miles of shoreline, citing danger from debris.
National Weather Service meteorologist Derek Wroe said Saturday that the surf peaked Friday afternoon and was slowly declining. However, a high surf warning remained in effect.
A storm about 1,500 miles to the north and northwest of Oahu was sending large swells to the islands, he said.
The helicopters belonged to Marine Heavy Helicopter Squadron 463 of the service's 1st Marine Air Wing in Hawaii. Known as Super Stallions, they are the U.S. military's largest helicopter, capable of carrying a light armored vehicle, 16 tons of cargo or a team of combat-equipped Marines, according to a Marine Corps website.
The Coast Guard initially reported that the helicopters had collided, but Marine Captain Timothy Irish said Friday that he did not know whether there had been a collision.
The helicopters normally carry four crew members, but this particular flight also carried one or two instructor trainers, Irish said. He did not know whether they were teaching the crew or just observing.
Authorities were hopeful that survivors would be found.
"Thoughts & prayers are with our Marines & their families in Hawaii as search efforts continue," General Robert Neller, commandant of the Marine Corps, said on Twitter.
Some information for this report came from AP.