No survivors have so far been located and bodies have been found after a helicopter ferrying North Sea oil platform workers crashed off the coast of western Norway, Norwegian emergency services and police said Friday.
"We have found dead bodies, but can't give any numbers," duty officer Morten Kronen with the Bergen police told the Bergens Tidende daily.
Initial reports said there were 11 passengers and two crew members onboard.
The Joint Rescue Coordination Centre for southern Norway said a large search and rescue operation was underway, partly at sea and on land.
"The rotor blade has been found, while parts of the helicopter have been located six, seven metres under the water line," said Anders Bang Andersen, spokesman for the Joint Rescue Coordination Centre in Sola.
He told reporters that a distress signal was registered shortly after noon (1000 GMT), triggering the search and rescue operation.
Local broadcaster NRK earlier showed images of smoke billowing from the crash site near Turoy, about 40 kilometres from the city of Bergen. The fire was later extinguished.
The helicopter was heading for Bergen from the Gullfaks B oil platform that is operated by Norwegian energy company Statoil.
A Statoil spokesman said the company has mobilized its emergency response team, and set up an emergency hotline.
Local newspaper Stavanger Aftenblad reported that the helicopter was operated by the firm CHC Helicopter Service, and was a Eurocopter model EC225.
Norwegian Prime Minister Erna Solberg said on Twitter she was being briefed about the accident.
A witness, Jon Sekkingstad, told NRK he heard a loud bang, and saw the main rotor blade fly off from the helicopter, and an explosion when it hit the ground.
Helicopters and boats have been deployed to the scene. Part of the the wreckage was located on a small island, and also in the sea.
The Norwegian defence forces deployed three vessels and four divers.
The airspace around the crash site has also been closed for non-authorized aircraft, including drones, local police said.