A helicopter crashed into the North Sea while returning from an offshore oil rig on Wednesday, and all 16 people on board were feared to have been killed, British officials said. Police said eight bodies had been recovered but that search operations had been suspended until daylight on Thursday for the eight other people who had been on the Super Puma helicopter. There were "increasing and grave concerns" for the eight still unaccounted for, said a police spokesman. The search operation involved 15 ships and lifeboats. Oil company BP said the helicopter was carrying 14 passengers and two crew from its Miller platform about 165 miles offshore. Drilling company KCA Deutag said 10 of its workers were among the passengers, of whom nine were British and one was from elsewhere in Europe. A coastguard spokeswoman said flying conditions were excellent when the helicopter went down about 15 miles off the coast of Scotland. "There is nothing to suggest the weather would have had any impact at all on the actual incident," she said. It was the second Super Puma helicopter crash in the North Sea in six weeks. In February all 18 people on board a Super Puma traveling to a BP oil rig were rescued after the helicopter crashed into the sea after hitting a fog bank. Both helicopters were operated by Bond Offshore Helicopters, which runs a fleet of twin-engined Super Pumas to supply sea-based oil rigs. The RMT union called for the helicopter model involved in Wednesday's crash -- the Super Puma AS 332L -- to be grounded pending an investigation. One of Britain's worst North Sea helicopter accidents occurred in 1986 when a Chinook crashed near the Shetland Islands to the north of Scotland, killing 45 oil workers.