Four people are thought to have died after a helicopter carrying oil workers ditched into the North Sea.

Two bodies were recovered from the sea, one person died on the way to hospital and one other body is said to be still in the wreckage, according to Sky sources.

The Super Puma L2 aircraft went down at 6.20pm on Friday around two miles west of Sumburgh airport as it was returning to Shetland from the Borgsten Dolphin platform.

The helicopter was carrying 16 workers and two crew.

One of the rescued workers is moved on a stretcher

A search operation involving coastguard, police, RAF and local lifeboats was launched and 14 people rescued from the sea are now in hospital.

The helicopter is reported to be in several pieces but the wreckage has now been secured by the RNLI (Royal National Lifeboat Institution).

Helicopter operator CHC, which operates in 30 countries, said on its website that it was suspending all Super Puma L2 flights worldwide.

An RNLI spokesman said two of the dead were recovered by a lifeboat crew from Lerwick, Shetland.

Some of those rescued were able to walk unaided after the rescue

“The lifeboat crew transported the bodies to Sumburgh and we are liaising with other authorities as things develop, ” he said.

“Obviously this is the news that everyone, included our lifeboat volunteers, dreaded – our thoughts and prayers are with the families and loved ones of those concerned.

“We can also confirm that one of our lifeboats has also been involved in reclaiming wreckage from the scene as part of the operation.”

Amanda Smith, the mother of one of the workers Sam Smith, said her son had telephoned her from hospital after suffering cuts in the crash.

She told Sky News: “He said it seemed to lose power and there was no time to brace, they just dropped into the sea.

Helicopter crash off Shetland islands
A coastguard boat searches the North Sea

“He was by the window so he was able to escape that way as it rolled over.

“He said he had come off better than a lot of people. It didn’t seem real, I would say two hours later it’s just beginning to sink in.”

Helicopter operator CHC said it was flying for oil company Total and that the aircraft lost communication as it approached the airport on the southern tip of Shetland’s main island.

A spokesman said: “The aircraft was on approach to Sumburgh Airport at approximately 6.20pm when contact was lost with air traffic control.

“We can confirm there were 16 passengers on board, and two crew.”

Helicopter crash off Shetland islands
Several helicopters have been involved in the search operation

Investigators from the Air Accidents Investigation Branch are travelling to the scene.

Police Scotland said a major incident had been declared. Sumburgh Airport was closed to allow emergency services to deal with the ongoing incident.

A spokesman said all those rescued had been taken to Gilbert Bain Hospital in Lerwick.

Jim Nicholson, RNLI rescue co-ordinator, said the helicopter was in an “inaccessible” position and that weather in the area was not “particularly good”.

He said: “There was a fresh wind, not overly strong, visibility is not particularly good and it was misty in the area but I doubt if that would have had any impact on causing whatever happened to the helicopter.

“I believe that the helicopter is in a fairly inaccessible position at the moment near the cliffs. There’s quite a lot of tide in that area so any person in the water could be carried some distance away.”

Last year, two helicopters ditched in the North Sea only six months apart.

All passengers and crew were rescued in both incidents, which were found to be caused by gearbox problems.

The Unite union’s Scottish Secretary, Pat Rafferty, called for an urgent investigation.

“This is an absolute tragedy,” he said.

“This is the fifth major incident in the last four years involving Super Puma helicopters in the UK offshore industry and the second resulting in fatalities.

“It’s unacceptable and it can’t go on.”

He added: “A full investigation must now take place and the industry’s helicopter operators must use every means at their disposal to demonstrate that its fleet is fit for purpose.”