Norwegian oil rig support vessel capsized off northern Scotland. A coast Guard helicopter and navy divers are trying to find five crewmen missing.
Three people were confirmed dead after Thursday's accident, the coast guard said. Seven other crew members were rescued and were being treated at a hospital in the Shetland Islands.
The Bourbon Dolphin capsized west of the islands, off Scotland's northern tip.
All the crew members were Norwegian. Britain's Press Association news agency reported that a 15-year-old boy, aboard the vessel on a work-experience placing with his father, was among the missing.
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 at the scene and preparing to search inside 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.
Bourbon Offshore Norway said it had chartered a plane to take relatives of the crew, along with Norwegian police, company officials and religious ministers, to Shetland on Friday.