Shell has shut down an oil field off the coast of Nigeria after a leak during a transfer of oil to a tanker led to a spill of 40,000 barrels into the Atlantic Ocean.
The Bonga field is approximately 120km offshore. It produces 10% of Nigeria's oil exports.
Shell said the flow of oil from the leak had now stopped and no-one had been injured.
The company apologised for the leak and said it is focusing on the clean-up.
The BBC reports most previous oil spills in Nigeria have been onshore and caused by sabotage or rebel attacks.