Syncrude said the fire at its Mildred Lake facility north of Fort McMurray was extinguished early Thursday morning.

One day after a worker was seriously injured in an explosion and fire at Syncrude's Mildred Lake upgrader facility in northern Alberta, the company says it's found the cause of the blaze.

Syncrude Canada confirmed it was responding to a fire at its Mildred Lake Upgrader north of Fort McMurray Tuesday afternoon.

Canadian Oil Sands Ltd. is expecting the Syncrude oilsands development north of Fort McMurray, Alta., to return to normal production rates toward the end of the month.