Authorities say a helicopter carrying four people has crashed into an icy lake in southeast Romania. One person was rescued and a search is underway for the other three.

The chopper plunged into the Siutghiol Lake near the Black Sea on Monday afternoon, carrying a pilot, a co-pilot, a doctor and a nurse.

Interior Ministry official Raed Arafat said the doctor was rescued and transported to a hospital in serious condition.

Divers and rescue workers were looking for the other three at the crash site, 250 kilometers (155 miles) east of Bucharest. The search was hampered by frigid temperatures and darkness.

Arafat said the cause of the accident was not immediately known.