EDMONTON - Regulators are investigating the cause of a breach in a pipeline that leaked a half million litres of watery oil in northwest Alberta.

The Energy Resources Conservation Board says some of the Oct. 7 spill from the Penn West Exploration (TSX:PWT) oil well line got into a creek south of the community of Swan Hills.

The board says the company has since recovered more than five million litres of water that was contaminated by the spill and 2,300 tonnes of soil from the area.

Calgary-based Penn West says the leak was from an emulsion line that carries unprocessed watery oil from old oil wells for processing.

The energy board says the breach has been repaired and the facility is once again operating.

The board issued a news release about the breach on Oct. 9, but did not include the amount of watery oil that was spilled.