Oslo (AFP) - A helicopter carrying North Sea oil workers crashed off the coast of southwest Norway on Friday, killing all 13 people on board, rescue services said.
The Super Puma chopper went down around midday in the archipelago off the coast of Bergen, Norway's second-biggest city.
Rescue services recovered eleven bodies but called off the search for the two remaining passengers five hours later saying they could not have survived the crash.
"We presume that all 13 are dead," Borge Galta, head of the rescue centre in the southwestern Sola region told AFP.
The cause of Norway's worst helicopter accident in decades was not immediately known, but investigators seemed to be leaning towards a technical problem.
The aircraft was carrying 11 Norwegians, one Briton and one Italian, rescue services said.
The helicopter broke into pieces near a small island and debris was found scattered on land and at sea. Part of the chopper containing the bodies of some of the victims was resting on the seabed under five to seven metres (16 to 23 feet) of water, around 20 metres from land, rescue officials said.
The aircraft's black boxes were later retrieved, Dagbladet newspaper reported.
A spokesman for Sola rescue centre, Anders Bang Andersen, told AFP the helicopter had been on its way to Bergen's airport when it crashed with 11 passengers and two crew members on board.
It was returning from the Gullfaks B platform, in one of Norway's biggest offshore oil fields, which is operated by state-owned Statoil.
The chopper was an EC225 Super Puma built by Airbus Helicopters and operated by CHC Helikopterservice for Statoil.
Airbus Helicopters in a statement sent its condolences to the victims' families and said it was "fully mobilised" to understand the cause of the accident.
Norway's civil aviation authority said it had grounded all EC225 helicopters until further notice, recalling that the same model had encountered technical problems in 2012 which had led to restrictions on its usage.
Statoil set up an emergency help centre in Bergen for the families of the victims.
- Chopper was due inspection -
Verdens Gang newspaper reported that the owner of the helicopter, CHC Helikopterservice, had twice obtained a postponement of a scheduled technical inspection of the stricken helicopter.
Several witnesses described blasts and seeing the aircraft spiral downwards.
"There was an explosion and a very peculiar engine sound, so I looked out the window. I saw the helicopter falling quickly into the sea. Then I saw a big explosion," an island resident told the Bergensavisen daily.
"Pieces (of the helicopter) flew into the air," she said, adding that she saw the rotor detach. Mobile phone footage broadcast by TV2 channel showed it flying through the air.
A spokesman for Norway's accident investigation board, William Bertheussen, said investigators were trying to protect the crash site to get a full reading of the cause of the accident.
The crash was the deadliest of its kind in Norway since 1978, when a chopper plunged into the sea, killing 18 people.
"It's a very sad day for those who work in the oil and gas sector," Prime Minister Erna Solberg told a press conference, fully clad in black.
Live footage shortly after the crash showed leisure boats rushing toward the scene, where thick black smoke was billowing into the sky.
Helicopters, ambulances and divers were scrambled to the scene.
On August 23, 2013, a Super Puma AS332 L2, an older model of the same helicopter, crashed into the North Sea near the Shetland Islands, killing four.
Gullfaks, one of Norway's biggest offshore oil fields, suspended its drilling operations until further notice.