Four people who died after a helicopter plunged into the sea off Shetland have been named.
They were Duncan Munro, 46, from Bishop Auckland; Sarah Darnley, 45, from Elgin; Gary McCrossan, 59, from Inverness; and George Allison, 57, from Winchester.
Three of the four bodies have been recovered, and work is underway to recover the fourth. Fourteen others have been rescued and taken to hospital, a spokeswoman from Police Scotland added.
The Super Puma L2 aircraft had a "catastrophic loss of power," according to an RNLI official, before crashing two miles west of Sumburgh, on the southern tip of Shetland, at 6.20pm on Friday night.
The helicopter was carrying oil workers, returning to Shetland, north east of the Scottish mainland, from the Borgsten Dolphin platform in the North Sea.
Two bodies were recovered by a lifeboat crew from Lerwick, according to Jim Nicholson, RNLI rescue co-ordinator. He said the two bodies were recovered in the area the helicpoter crashed.
"The bodies came to the surface close to the helicopter wreckage," he said.
"The helicopter was in a pretty inaccessible place but the lifeboat crew were able to get to them using an inflatable craft. It's fortunate there were not more casualties in a helicopter crash of this kind.
"There appears to have been a catastrophic loss of power which meant the helicopter suddenly dropped into the sea without any opportunity to make a controlled landing."
A major search operation, involving the coastguard, police, RAF and RNLI, was extended overnight in order to find those who remained missing.
The rescue team spent hours securing the helicopter and moving it to a more accessible location as it waits to be loaded on to a vessel so it can be searched.
"It may be that a body is recovered on the helicopter," Mr Nicholson added.
While the exact condition of all the casualties is not known, Sky News reports that eight of them were able to walk off the rescue aircraft.
All 14 survivors, including two crew members, were taken to Gilbert Bain Hospital in Lerwick to be treated.
One of the men rescued, Sam Smith, described how the helicopter suddenly lost power and leaving those on board "no time to brace", it has been reported.
His mother Amanda Smith told Sky News: "He said (the helicopter) seemed to lose power and there was no time to brace - they just dropped into the 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, were his words.
"It doesn't seem real."
The coastguard said the aircraft's life rafts were found empty and wreckage from the aircraft has begun to wash up at the southern end of Sumburgh.
The helicopter's 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 CHC spokesman said, "The aircraft was on approach to Sumburgh Airport at approximately 6.20pm when contact was lost with air traffic control."
In addition to the two lifeboats from Lerwick and Aith, helicopters from the coastguard, RAF Lossiemouth and two Bond rescue helicopters were on the scene providing assistance.
A Northlink ferry carrying 201 passengers between Shetland and Orkney was also diverted to the scene to help.
Scotland's First Minister, Alex Salmond, has paid tribute to all those involved in the rescue effort.
In a statement he said, "Our thoughts at this difficult time are with the families, friends and colleagues of those who lost their lives in this tragic incident. We also hope that those who were injured can make a full and speedy recovery.
"I would like to pay a massive tribute to all of those brave and hard-working individuals involved in the rescue effort and in treating the casualties when they were brought ashore."
"It is still too early to know what caused this terrible tragedy, but a full investigation by the relevant authorities is already under way.
"The Scottish Government is in regular contact with all the agencies who have been involved in this rescue and recovery operation through our Resilience process."
Aberdeen Council have announced that they will be flying the flag outside the Town House, the local authority's offices, at half mast in a mark of respect to those who have lost their lives.
Lord Provost of Aberdeen, George Adam, said, “Everyone in this city knows someone who works offshore and so this tragedy hits home with us all.
“It is easy to take for granted the fuel that powers our everyday lives, but we cannot forget the enormous gratitude we owe to these friends, relatives and colleagues who work in such a challenging environment.
“We have a close knit community here, and I know that the heartfelt sympathies of the whole city go out to everyone affected.”
The Moderator of the General Assembly of the Church of Scotland, the Right Reverend Lorna Hood, said: “We offer our deepest sympathy and heartfelt sorrow as we pray for all those grieving loss this morning.
“We also offer our gratitude for the bravery of all those involved in the rescue and are reminded once again of the perilous nature of work in the oil and gas industry.
“I will be in touch with our Chaplain to the Oil and Gas Industry the Rev Gordon Craig. I am sure he will be offering his help and support in the aftermath of this incident.”
The families of those affected have been informed.
Such helicopter accidents in the area are not uncommon. Last year, two helicopters ditched in the North Sea within six months with gearbox problems being found to be the causes. All passengers and crew were rescued in those incidents.
The Guardian reports that Jake Molloy, the Aberdeen-based regional organiser of the Rail, Maritime and Transport Workers union (RMT) said there had been concern among members following the two incidents.
"We need to wait to determine what forced the aircraft down. Quite clearly it's the last thing we need at this point in time," Molloy said. "I would understand completely if people did not want to get aboard these aircraft. In my opinion these aircraft should not be flying until we establish the circumstances to this very serious incident."
In April 2009, 16 people died when another Super Puma helicopter plunged into the sea following a gearbox failure on its way to Aberdeen.