BP plc is still working to secure a well in Alaska’s Prudhoe Bay field that began leaking hydrocarbons last Friday. An oil leak has been stopped, but a natural gas leak continued Monday.

“Based on an overflight with infrared cameras, the release appears to be contained to the gravel pad surrounding the wellhead and has not reached the tundra,” the company said in a statement issued Saturday, the most recent available from BP as of early Monday morning in Alaska.

The leak is at the BPXA Drill Site 2 (DS2) pad, Well 3, and oil and natural gas well, in the Greater Prudhoe Bay area, about five miles from the Deadhorse Airport, according to a Sunday update from the Alaska Department of Environmental Conservation (DEC).

BP Exploration Alaska (BPXA) employees discovered an uncontrolled gas release from the top of a well house on Friday morning. A crude oil spray was confirmed and the spill was reported to authorities.

“The well is currently venting gas, which caused an initial spray of crude oil that impacted the well pad,” DEC said. “However it is not currently spraying crude oil. A Forward Looking Infrared overflight shows that the crude spray plume did not leave the pad; however, the situation is not safe yet for responders to access the area and confirm that there have been no impacts to adjacent tundra.”

The cause of the release is not yet known. DEC is coordinating with BPXA and the Alaska Oil and Gas Conservation Commission to investigate the cause.