BP has had a pipeline leak at its Alaskan oilfields, the latest blow to its reputation after the Gulf of Mexico oil spill.
A pipeline at BP's 30,000 barrel per day Lisburne field, currently closed for maintenance, ruptured during testing this weekend, spilling a mixture of methanol and oily water onto the tundra.
It is the latest in a long history of oil spills at the BP Alaskan pipelines, where around 40 per cent of its assets are based.
The Alaska Department of Environmental Conservation said the spill amounted to 2,100 to 4,200 gallons.
A BP spokesman said the cleanup was under way and the company would determine the cause "in due course".
Lisburne, which is managed as part of the Greater Prudhoe Bay Unit, has produced no oil since June 18, according to Alaska Oil and Gas Conservation Commission records, suggesting maintenance work requiring a prolonged shutdown.
The field had been undergoing "its annual maintenance", the BP spokesman said.
BP's blown out Macondo well caused the worst offshore oil spill in U.S. history, spilling almost five million barrels of oil into the Gulf of Mexico and putting BP's future in the U.S. at risk.
Previous problems including leaks from corroded pipelines in Alaska and the fatal Texas City refinery blast in 2005 had already earned the company a poor reputation for safety, something analysts say it needs to address if it is to continue to grow in North America.
Production from the entire Lisburne field remains shut off while the spill is addressed, Alaska officials said.
Immediate efforts are focused on containment and cleanup, said Tom DeRuyter, state on-scene coordinator for the Department of Environmental Conservation.
The methanol-produced water mix has spread into wet tundra as well as onto a gravel pad, bringing risks to slow-growing vegetation, DeRuyter said.
The pipeline will also have to be dug up to allow for an investigation into why it failed, and normal operations on the part of the field may take a while to resume, he added.