A pipeline operated by a Texas-based oil company has leaked 9.5 million litres of industrial waste water in northern Alberta.

The Energy Resources Conservation Board said the spill was first reported by Apache Canada Ltd. on June 1.

The pipeline breach is about 20 kilometres northeast of Zama City, a remote community near the Northwest Territories boundary.

Apache said it has stopped the leak and is working to contain and clean up the spill that covers a 42-hectare area.

Waste water that is extracted during oil and natural gas operations contains oil, salt and other minerals.

Apache said the nearby Zama River has not been affected by the spill.

Alberta government spokesperson Jessica Potter said some of the waste water made its way into tributaries that feed into the Zama.

"There's ongoing water monitoring and that information is being fed to labs," she told CBC. "That information is useful to determine how in the future, the soils, if necessary, need to be remediated. So right now it does take some time to properly assess the impacted area."