A faulty gasket is to blame for the 230,000 liters of oil discovered Monday spilling from Enbridge's Athabasca pipeline, says a spokesman for the Energy Resources Conservation Board.

About 1,445 barrels of heavy crude oil leaked out of the pump station where the gasket was located. The 541-kilometre pipeline stretches from the Fort McMurray oil sands to Hardisty and has a capacity of 345,000 barrels per day.

Enbridge spokesman Graham White said it is not possible to offer an estimate of the area affected by the spill because "some areas are more affected than others."

"The area affected is our pump station site, some area along the pipeline right-of-way that is also (owned by) Enbridge and part of a local field," White said in an email Wednesday. "The vast majority of the spill is on the site and there is no impact to waterways or wildlife."