A technical problem at BP's Clair platform in the North Sea resulted in a spill of 95 tonnes of oil that was allowed to disperse naturally into the sea, the British oil major said on Monday.
Production at the platform, located 75 km west of the Shetland Islands, was halted after the incident which took place on Sunday.
BP said it was working together with oil spill and environmental experts from BP, Oil Spill Response Limited (OSRL) and the Department for Business, Energy and Industrial Strategy (BEIS) to assess any potential environmental impact and to agree the best way to respond.
"At present, we believe the most appropriate response is to allow the oil to disperse naturally at sea, but contingencies for other action are being prepared," BP said in a statement.
The most likely volume of oil that went into the sea during the hour-long spill has been calculated from platform data as around 95 tonnes, BP said.
By comparison, an average Suezmax tanker carries around 100,000 tonnes of oil.
"Both direct observation from surveillance flights and oil spill modelling continue to show the oil moving in a northerly direction away from land."
The most recent surveillance flight already indicates significant dispersal of the oil at the surface.
Britain's BEIS said it would hold an investigation to determine the cause of the incident, which is standard procedure.
"We are working closely with BP and the Maritime and Coastguard Agency to resolve the incident on the Clair platform," a spokesman said.
There have been no reported injuries, the department added.
(Reporting by Ron Bousso and Karolin Schaps; Editing by David Goodman and David Evans)