An oil spill that went undetected for days has released 22,000 barrels of oil into northeastern Alberta’s muskeg, news sources report.

The spill, an emulsion composed of oil and water, came from a waste disposal line owned by Pace Oil and Gas, and was evidently only discovered when an aircraft from another oil company made a routine flyover in the area on May 19, the Calgary Herald reports.

The spill is “among the largest in North America in recent years,” reports the Globe and Mail.

Pace Oil and Gas has set up a 50-person camp near the spill, which is located about 20 kilometres southwest of Rainbow Lake, in northern Alberta, the Globe reports. The company has built trenches around the site and oil-skimming equipment has so far recovered about 11 per cent of the emulsion, according to company spokespeople.

This is the second major oil spill in Alberta in a year. Last year, the Rainbow pipeline, owned by Plains All American Pipeline, spilled 28,000 barrels of oil into northern Alberta’s forests.

Also last year, Alberta-based Enbridge struggled with an oil leak from a pipeline in Michigan, after a two-vehicle collision damaged an above-ground portion of the pipe.

Regulators told the Herald that spills like the one at Rainbow Lake are infrequent, despite the large volume of oil that moves out of the province every day.

"These types of spills are rare," Darin Barter of Alberta's Energy Resources Conservation Board told the Herald.

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