Two military helicopters, each carrying six U.S. soldiers from the Kaneohe Bay U.S. Marine Corps Air Station in Hawaii, reportedly collided in midair Thursday night over water north of the island of Oahu.

The Coast Guard-led search and rescue operation for the 12 marines has been underway since midnight. They have uncovered fire, debris, and an empty life raft about two and a half miles north of Oahu, though no survivors have been found as of 8 a.m. Eastern.

The 12 marines were engaged in a training exercise at the time of the crash, though no information is currently available on the cause of the collision.

Rescue attempts will have to contend with some of the most significant ocean swells of the season on Friday. Some are forecasting waves as high as 40 feet.

Check back here for updates as details become known