United Kingdom oil giant BP has been engaged in controlling a damaged oil well on Alaska's remote North Slope over the weekend, after the well started venting natural gas vapours on Friday morning, according to the company and Alaska officials.
The volume of the leak hasn't been determined and the cause of the release is unknown, the department said.
In 2010, a BP well became the site of the worst offshore oil spill in US history.
Clanton said BP is focused on safely securing the well. "The bottom leak has been reduced, but is now leaking gas as well as some minor amount of crude oil".
A BP drill site in Prudhoe Bay has been depressurized after employees at the facility discovered an "uncontrolled gas release" from the top of a well house Friday morning, according to the Alaska Department of Environmental Conservation.
The well is too unsafe at this time for a response team made up of state and federal energy officials and BP employees to get near the well.
But the platform is still venting gas from a leak associated with a damaged pressure gauge.
The public image of BP is still recovering from the 2010 explosion and oil spill in the Gulf of Mexico, which killed 11 people and affected beaches and wetlands. The upper leak was the one leaking crude oil and hazardous natural gas, but a safety valve activated and shut that leak off. There have been no injuries and no reports of harm to wildlife.
BP had a 201,000-gallon oil spill in March 2006 and a smaller spill five months later that ultimately caused it to halve production at Alaska's Prudhoe Bay for several weeks.
But the release of vented natural gas means that the well is still leaking methane, a potent greenhouse gas that traps heat 86 times more effectively than carbon dioxide over a 20-year period, into the atmosphere.