The Coast Guard was alerted late yesterday to the reported collision between two Marine Corps choppers carrying six crew members each, said Coast Guard spokesman Sara Mooers from Honolulu.
Coast Guard search aircraft have spotted a debris field about four kilometres off the north shore of Oahu but no people, she said.
The Coast Guard sent a helicopter and an HC-130 Hercules plane to take part in the search. Also searching are a Navy helicopter and one from the Honolulu fire department, as well as a rescue boat, Mooers said.