OSLO A helicopter ferry passengers crashed in the North Sea on Friday, killing at least 11 of the 13 people on board, rescue officials said.
"The helicopter is completely destroyed," it said. After searching for several hours survivors, 11 bodies were found and the remaining two people were supposed dead.
Norway and Britain perched commercial flights of the type of helicopter concerned in the crash, an Airbus Helicopters H225 Super Puma, a workhorse of the offshore oil industry.
Several witnesses told Norwegian media they saw the rotor blades separating from the helicopter while still in the air.
"While I looked up, the rotor (blades) loosened and disappeared towards the north," John Atle Sekkingstad told the website of local paper Bergens Tidende.
"After that, the helicopter turned north and I saw fire at the top of the helicopter, where the rotor had been attached. It caught fire before it crashed."
The main body of the aircraft was lying under water, while its rotor was found on a rocky outcrop about 200 to 300 metres (220-330 yards) away, state broadcaster NRK said, quoting the rescue centre.
Oil worker Chris Andersen told NRK: "I saw the rotor separate ... It was horrible. There was a huge explosion that you could physically feel. You felt the vibrations."