"We are deeply concerned with this," said Ron Bailey, Nexen's senior vice-president of Canadian operations. "We sincerely apologize for the impact this had caused."
The spill was discovered Wednesday afternoon at Nexen Energy's oilsands facility near Long Lake, south of Fort McMurray.
The material leaked through what Bailey says was a "visible burst" in the pipeline. a double-walled, high-pressure line installed in 2014. Bailey said the line was shut down immediately after the leak was discovered.
The detection system did not work in this case, so it isn't known how long the pipeline was leaking. A contractor walking along the pipeline discovered the leak.
"This is a modern pipeline," Bailey said. "We have pipeline integrity equipment, some very good equipment," he said. "Our investigation is looking through exactly why that wasn't alerting us earlier."
The spill covers an area of about 16,000 square metres. Bailey said it is mostly contained within the pipeline right of way.
The area can only be reached by a winter access road, so the company had to build a road into the site. Bailey said the vacuuming of the oil is starting today. The site is contained by berms and other abatement equipment.
Despite the scope of the incident, Alberta Premier Rachel Notley said pipelines are still the best way to transport oil and gas.
"For instance, in Quebec, they know full well that rail is much more problematic a transportation method," Notley told CBC's Edmonton AM on Friday.
"Even within this unfortunate accident, which I'm troubled by."
Notley is attending the Council of the Federation meeting in St. John's, where premiers agreed to a national energy strategy.
She said her government is getting regular updates about the spill.
"We'll be doing an investigation into what went wrong and what happened with respect to how long the leak was in place and whether everything was done to catch it as soon as it could be, as well as to prevent it at the outset," she said.
"Unfortunately, there's nothing we can say except that we are going to learn from this."
In April 2011, a Plains Midstream Canada ULC pipeline leaked 4.5 million litres of crude oil near a First Nations community in northwest Alberta.
That leak was the largest in the province in 35 years. It contaminated more than three hectares of beaver ponds and muskeg in a densely forested area.