BP has spilled hundreds of barrels of oil in the North Sea, in a leak from its Clair platform.
The energy giant said the leak was stopped within an hour of being spotted on Sunday morning and it had temporarily shut down the platform, 46 miles west of Shetland, while it investigated the precise cause.
It estimated that 95 tonnes of oil, equivalent to more than 665 barrels, had been released during the leak, which left oil visible on the surface of the sea.
BP said that the slick appeared to be moving northwards away from land and it believed that "the most appropriate response is to allow the oil to disperse naturally at sea", though it was preparing "contingencies for other action".
A spokesman said the leak had been caused by "a technical issue with the system designed to separate the mixed production fluids of water, oil and gas".
"We are investigating the cause of the technical issue and the field will remain offline until the investigation is concluded," he added.
BP is working with Oil Spill Response Limited and the Department for Business, Energy and Industrial Strategy to "assess any potential environmental impacts and to agree the best way to respond".
The leak comes at an embarrassing time for BP as it coincides with the release of the film Deepwater Horizon, about its disastrous oil spill in 2010, which spewed more than 3m barrels into the Gulf of Mexico.
The company has battled to improve its safety reputation. Last year Shell was fined £22,500 over the 2011 leak of 216 tonnes of oil from its Gannet Alpha platform in the North Sea.
A BEIS spokesman said: "Safety is the Government's number one priority. We are working closely with BP and the Maritime and Coastguard Agency to resolve the incident on the Clair platform."