Us helicopters
U.S. military helicopters fly as a group over Camp Pendleton, Feb. 23, 2015. Two military helicopters collided late Thursday off the coast of Oahu, Hawaii. Reuters / Mike Blake

UPDATE 2:05 p.m. EST: Crews continued to search Friday for a dozen Marines who were missing at sea off the coast of the Hawaiian island of Oahu after an apparent collision of two CH-53 helicopters during an overnight training flight, according to CNN. The Coast Guard's search for survivors has continued despite further complications from increasingly poor weather, Marine Maj. Christian Devine said to the news station Friday.

The responders were searching for the missing Marines amid rough seas and overcast skies. "The North Shore is famous for its big wave surf,” Chief Petty Officer Sara Mooers of the Coast Guard in Hawaii said to the New York Times. "Being in that kind of condition, if you are without a board, I don’t know what that would be like."

Residents in the area told Hawaii's KHON2 that the crash felt like an earthquake. Witnesses said to the news station that they heard a "boom over the water and saw a big flare in the sky."

UPDATE: 9:03 a.m. EST -- The U.S. Marine Corps confirmed on Twitter Friday morning there was an active search and rescue effort underway for two Marine aircraft, following reports of a collision off the shore of the Hawaiian island of Oahu. The Marine Corps said the two aircraft were CH-53 helicopters.

It was earlier reported that 12 people were aboard the two aircraft.

Original Story:

The U.S. Coast Guard was searching for survivors Friday after two military helicopters collided off the north shore of the Hawaiian island of Oahu late Thursday, according to multiple reports. Twelve people were aboard the two aircraft.

Rescue teams were combing through a debris field some 2 miles off the coast of Haleiwa, ABC News reported. CNN reported responders spotted a fire and an empty life raft among the debris, citing Chief Petty Officer Sara Mooers of the Coast Guard. Waves that measured 40 feet were limiting rescue efforts, UPI reported.

ABC News reported the Coast Guard received a call at 11:38 p.m., local time (4:38 a.m. EST), Thursday requesting help at the Marine Corp Air Station, Kane’ohe Bay. Officials sent out two Coast Guard aircraft in response, an MH65 helicopter and an HC130 Coast Guard airplane.

The Coast Guard's search and rescue efforts are being conducted with assistance from a Navy helicopter crew and the Honolulu Fire Department. No military personnel have yet been found in the search for survivors.