Click to view 3 other videos:  Questionable pipeline ruptures in Alberta near native settlement:

 

The spill was discovered Wednesday afternoon at Nexen Energy's oilsands facility near Long Lake, south of Fort McMurray.

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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 substance was leaking. A contractor walking along the pipeline discovered the spill.

 

Ron Bailey, senior vice president of Canadian operations for Nexen, apologized for the spill. (CBC)

"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.