Canadian authorities have begun airlifting up to 25,000 people to safety from the oil city of Fort McMurray, where a wildfire has destroyed some 2,000 homes.

Eight thousand people were airlifted out of the region on Thursday, and the evacuation operation is to continue on Friday with further air rescues and a planned mass convoy of cars if the highway south is deemed safe.

Authorities on Tuesday ordered the city of 100,000 people to be evacuated after firefighters backed by air tankers and helicopters failed to contain the huge blaze, which has engulfed 12,000 hectares (29,652 acres) in the area surrounding Fort McMurray, now the epicenter of the fire. The airlift was launched after it became apparent that some 25,000 evacuees who found refuge north of the city risk becoming trapped if shifting winds were to cause the wildfire to head in their direction.

But the bulk of the evacuees fled south, from where officials are trying to move them even further in the same direction to places where there are better support services.

The flames have now burnt out 85,000 hectares (210,000 acres) in the province, which is the size of France and home to one of the world's largest oil industries. The Alberta provincial government said more than 1,100 firefighters, 145 helicopters, 138 pieces of heavy equipment and 22 air tankers were involved in fighting the fires.

In total, 49 separate fires were burning across the province, seven of them completely out of control.

So far, there have been no fire-related injuries or deaths.

Hope for rain

Alberta's manager of wildfire prevention, Chad Morrison, said the fire could not be extinguished without help from rain.

"Let me be clear: Air tankers are not going to stop this fire," he said. "It is going to continue to push through these dry conditions until we actually get some significant rain."

Forecasts from Environment Canada have predicted that there will be no rain clouds in the area around Fort McMurray until late Saturday, when there will be a 40 percent chance of showers.

Alberta has experienced a period of unusually low rainfall accompanied by unseasonably high temperatures, making the province tinder-dry and prone to fire.

Although the blaze is continuing to grow, the rate has slowed and it is gradually moving away from Fort McMurray. Despite this, residents have been warned that they may have to wait a long time before they can safely return.

Lawmaker Rona Ambrose, who represents the fire-ravaged region, said that it was "apparent that the damage to the community in Fort McMurray is extensive, and the city is not safe for residents at this time."

And Public Security Minister Ralph Goodale warned that such a disaster "will not be solved in a day or two, a week or two, or a month or two. We're all going to have to be here for the long haul."

tj/msh (AP, AFP)