BP began drilling at the massive Prudhoe Bay oil field in 1968.
An oil well leaking natural gas on Alaska's North Slope has been successfully plugged, according to private and government responders. Officials say oil likely spilled only on the well pad and not nearby tundra.
Alaska Department of Environmental Conservation spokeswoman Candice Bressler says the well operated by BP Exploration Alaska Inc., a subsidiary of BP, was successfully controlled overnight.
But the platform is still venting gas from a leak associated with a damaged pressure gauge. Environmentalists, describing the well as "out of control", called on the state to investigate. The Coastal Plain of the Arctic National Wildlife Refuge also contains vast reserves of oil - as much as 16 billion recoverable barrels, by some estimates.
The task force comprising BP, officials from the local government of the North Slope, the EPA, and the ADEP has been dealing with the spill since Friday.
Responders on Saturday night were able to enter the well house and connect hoses to valves.
The leakage from an oil well in the direction of the cold arid tundra plains in the north, but the volume of leaks so far is still unknown, the United States news network ABC News reported. This last March, daily output in the area hit 565,000 bpd - the highest in more than three years.
BP employees discovered an uncontrolled natural gas leak Friday at a well five miles from the Deadhorse airport. In 2006, a BP well in Prudhoe Bay spilled about 267,000 gallons of oil, the largest in the region's history.
The North Slope is also home to vast underground reserves of natural gas, but the lack of a gas pipeline out of the region has kept companies from bringing any of it to market.
There were no reports of harm to nature or injuries.