Officials said work was being done to clean up after an emulsion leak released fluids into the wilderness in northern Alberta.

Nexen said about 5 million litres of fluid – a combination of bitumen, water produced by the extraction process and sand – was leaked into an area about 16,000 square metres in size at Nexen’s Long Lake Project.

The site is located about 35 kilometres southeast of Fort McMurray.

The spill was first noticed Wednesday along the pipeline’s route – and apparently spilled into some muskeg.

Nexen said Thursday the site was under control, but the cause wasn’t clear – the company and the Alberta Energy Regulator (AER) are investigating.

“Our concern is public and certainly wildlife and environmental risks with an incident,” Peter Murchland with AER said in an interview with CTV News. “We’re pleased to report there’s no impact to the wildlife or the public with this incident.”

However, AER has asked Nexen to implement a wildlife protection plan in the area.

Nexen said in a statement that “all necessary steps and precautions have been taken” and the company will protect the health and safety of all employees, contractors, the public and the environment.

AER officials said this incident was one of the larger spills on record, the most recent spill nearing the same magnitude was in 2011 near Little Buffalo – where a Plains Midstream pipeline leaked about 4.5 million litres into marshlands in the area.

The province laid three environmental charges against the company for the spill.

With files from Danelle Boivin