NEW YORK (TheStreet) -- Shares of Canadian Oil Sands (COSWF) are down -4.44% to $20.88 on Friday after the oil-sands company announced unplanned maintenance work at the Syncrude Coker 8-1 mine, near Fort McMurry in Alberta, Canada, which caused the company to lower its estimated 2014 Syncrude production to 95 million-105 million barrels from 95 million-110 million.

The company said it will lower its guidance for 2014 when it releases its first quarter results on April 30.

As a result of the unplanned maintenance, National Bank of Canada downgraded the company's rating to "underperform" from "sector perform."

The firm believes the company will be hit "especially hard" during second quarter production because the unplanned outage at Coker 8-1 coincides with the scheduled maintenance of another upgrader.

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