Rescue helicopters scoured the frigid North Sea on Friday for signs of five crewmen missing after their Norwegian oil rig support vessel capsized off northern Scotland.
Three people were confirmed dead after Thursday's accident, the coast guard said. Seven other crew members were rescued and were being treated in a Shetland hospital.
The Bourbon Dolphin capsized west of the Shetland Islands, off Scotland's northern tip.
All the crew members wereNorwegian.
The coast guard said the five missing crew members may have been trapped in the hull of the upturned vessel, which was operating at the Transocean Rather rig when it capsized.
Authorities said there was only a slim chance they had survived.
Jim Sinclair, watch manager at Shetland Coastguard, said navy divers were preparing to search the upturned vessel, but that the search and rescue operation had become a search and recovery operation.
"It's a fairly complex and delicate operation because the vessel, as you'll appreciate, is upside-down and stability is uncertain so you'd want to make sure of your own safety before going under the hull," he said.
The ship capsized at about 5 p.m. (1600GMT) and remained on the surface of the calm ocean in clear weather about 75 nautical miles west of the Shetland islands, coast guard spokesman Mark Clark said.
The cause of the accident was not immediately known.
The ship is owned by Bourbon Offshore Norway AS. After the accident, 72 nonessential staff were evacuated from the oil rig, which is operated for Chevron Corp. by offshore drilling company Transocean.