Two US military helicopters collided off the coast of Hawaii early on Friday morning, according to reports.
The helicopters were carrying a total of 12 passengers when they crashed off the northern shore of Oahu island, CNN quoted the US Coast Guard as saying.
Rescue workers spotted a fire on the surface of the sea and a field of debris – including an empty life raft - according to Chief Petty Officer Sara Mooers.
CBS News reported the Coast Guard arrived just after midnight and found the debris roughly 2.5 miles off shore.
The news agency said there were six personnel on each helicopter, although this could not be immediately confirmed.
The aircraft had been dispatched from the Marine Corps Air Station on Hawaii's Kaneʻohe Bay.
The US Coast Guard is currently searching the debris for survivors assisted by a Navy helicopter crew and the Honolulu Fire Department, according to ABC News.
A helicopter and rescue boat were also on scene the news agency said. Rescue workers are understood not to have located any personnel so far and are continuing to search the water.
Efforts are being hampered by massive waves and strong currents, however. Surf in the area will be up to 30-40 feet high throughout Friday as the largest swell of the season rolls in, Hawaii News Now reported.
Video footage published by Khon2.com showed fire fighters and ambulances arriving at the scene in heavy rain.
