JUNEAU, Alaska (AP) — A U.S. Coast Guard helicopter on a search and rescue mission crashed in southeast Alaska, seriously injuring two of the four crew members on board.

All four crew members were taken to Seattle for treatment following the crash late Monday on Read Island, about 80 miles (129 kilometers) east of Sitka, said Coast Guard Lt. Cmdr. Michael Salerno. The Coast Guard described two of the crew members’ injuries as serious.

The crash was reported by the fishing vessel that was the subject of the search and rescue call that the helicopter was responding to, he said. The cause of the crash is under investigation, and Salerno had no further details about what might have contributed to the crash.

Rescue crews from state and local agencies and another Coast Guard helicopter arrived at the scene early Tuesday to help provide medical care to the crew members who were more seriously hurt, the Coast Guard said in a news release posted on social media.

The crash was reported about 11:05 p.m., and the first crews arrived about 12:50 a.m., the Coast Guard said.