A raging Canadian wildfire grew explosively on Saturday as hot, dry winds pushed the blaze across the energy heartland of Alberta and threatened to burn close to an oil sands project.

The fire, which has already prompted the evacuation of all 88,000 people who lived in the city of Fort McMurray, was set to double in size on Saturday, the seventh day of what is expected to be the costliest natural disaster in Canada's history.

Provincial officials praised evacuees for their patience and, in a sign of how long the crisis could drag on, said the cities of Calgary and Edmonton, many hundreds of kilometers to the south, were the best place to receive longer-term support such as medical care and emergency payments.