Get breaking news alerts and special reports. The news and stories that matter, delivered weekday mornings.

Two Marine helicopters with 12 air crew on board were involved in a mid-air collision off the coast of Hawaii, U.S. military officials tell NBC News.

The two CH-53 Sea Stallion helicopters were conducting a nighttime training mission at the time of the accident. The crash happened off the coast of Haleiwa, located on the North Shore of Oahu.

"This is still an active search and rescue operation," Capt. Tim Irish of Marine Corps Base Hawaii told reporters Friday afternoon.

Let our news meet your inbox. The news and stories that matters, delivered weekday mornings. This site is protected by recaptcha

The helicopters carried air crew and no passengers were aboard, Irish said. They were conducting “routine nighttime flying” and failed to return to base, he said. There was no distress call, officials said.

Coast Guard rescuers spotted a burning debris field in the water and at least one empty life raft, but so far have found no sign of any survivors. Rescue efforts were hampered by high seas, officials said.

Crews are searching an area seven miles offshore that stretches from Mokule’ia Beach to Turtle Bay, the Coast Guard said.

A safety zone has been established from Ka’Ena Point to Kahuku Point stretching seven miles out, Coast Guard Lt. Scott Carr told reporters. “That is a huge area. We have found debris across the entire area,” he said.

A Coast Guard MH-65 Dolphin helicopter and HC-130 Hercules plane and two cutters are involved in the effort, as well as military aircraft and ships and the police and fire department, Carr said.

"Everybody’s putting every available resource they have to try and find survivors from this accident," Carr said. "With a little bit of luck and a little bit of prayer, we’ll be successful."

The Marine Corps can confirm there is an active search and rescue for 2 CH-53's of the coast of Oahu. pic.twitter.com/3eIHloJYOx — U.S. Marines (@USMC) January 15, 2016

The cause of the crash has not been determined. According to the Weather Channel, there were light winds and scattered showers at the time of the collision.

Carr said winds of 10 to 20 knots, swells of 16 feet and surf of up to 30 feet were hampering the search and moving debris around.

The aircraft are from the 1st Marine Aircraft Wing from Marine Corps Base Hawaii.