* Alberta pipeline leak spills 5 million litres

One of the largest leaks in Alberta history has spilled about five million litres of emulsion from a Nexen Energy pipeline at the company's Long Lake oilsands facility south of Fort McMurray.

The leak was discovered Wednesday afternoon.

Nexen said in a statement its emergency response plan has been activated and personnel were onsite. The leak has been stabilized, the company said.

The spill covered an area of about 16,000 square metres, mostly within the pipeline corridor, the company said. Emulsion is a mixture of bitumen, water and sand.