A North Slope spill of an estimated 46,000 gallons was caused when a pipeline ruptured lengthwise along the bottom, creating a 2-foot-long opening.
A unified command of officials handling the spill say the rupture along the bottom of the 18-inch pipeline was caused by too much pressure in the line, likely caused by ice plugs.
The spill of crude oil, mixed with natural gas and water, occurred more than a week ago in the Lisburne field just north of the Prudhoe Bay oil field. The pipeline was not in operation at the time. When it ruptured, residual material spilled on to the tundra.
A visual inspection of the BP-operated line was delayed until it was completely depressurized. Inspectors got a look at it Monday. It is no longer leaking.