Reuters reported that output has been shut at Nexen's North Sea Buzzard oilfield after a weekend fire which has been extinguished, traders said on Monday.
The Buzzard oilfield, the UK's largest, is set to return to full production in 24-48 hours, traders said.
Nexen could not be reached for immediate comment.
A spokesman for the UK Health and Safety Executive said: ‘HSE is aware and an investigation has started’.
The oilfield normally pumps about 200,000 barrels of crude oil per day and feeds into Forties, one of the four key streams used for the North Sea price benchmark.