Honolulu fire, police and ocean safety officials are helping the Marines and the Coast Guard with the search for the 12 people who were aboard two Marine Corps helicopter that crashed during a nighttime training mission.
Military officials say the transport helicopters known as CH-53Es crashed late Thursday.
There's been no word on the fate of those aboard or what caused the accident.
The rescue effort has been hampered by rough seas in the area where debris was sighted.
The choppers were part of the 1st Marine Aircraft Wing at Marine Corps Base 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.