Trilogy Energy Corp. estimates a leak from its pipeline in west-central Alberta released 1,500 barrels of oil and water before it was discovered in early October.
The company announced the preliminary estimate Tuesday, the same day the Alberta Energy Regulator formally launched an investigation of the spill 16 kilometres northeast of Fox Creek, Alta.
The regulator said it would determine its own estimate of the size of the spill, which was made up of equal parts oil and produced water, and consider potential enforcement actions.
The AER said the pipeline has been shut down and is being purged, and that staff remain on site to ensure safety and environmental requirements are being met.
Trilogy said on Oct. 11 it estimates the affected area at three hectares, or about the size of five CFL football fields.
The company said it found two dead birds on site within the first 48 hours but has not reported any further wildlife affected by the spill.
With files from Canadian Press