A massive wildfire in Canada exploded tenfold in size, forcing the evacuation of 8,000 people from work camps north of Fort McMurray by air as the inferno grew to 850sq km.

Canadian officials said they would move thousands more via a highway convoy on Friday.

A government airlift of those cut off to the north began from oil facility airstrips. Alberta Premier Rachel Notley said some 4,000 people had already been airlifted to the cities of Edmonton and Calgary as of late Thursday.

The damage to the community of Fort McMurray is extensive and the city is not safe for residents," said Notley in a press briefing late on Thursday, as those left stranded to the north of the city clamoured for answers.

Evacuees from the Fort McMurray wildfires use a hockey rink full off beds as they sleep and rest at the "Bold Center" in Lac la Biche, Alberta [Mark Blinch/Reuters]

READ MORE: State of emergency as fire engulfs Canadian city


"It is simply not possible, nor is it responsible to speculate on a time when citizens will be able to return. We do know that it will not be a matter of days," she added.

Officials also warned that the communities of Anzac and Gregoire Lake Estates, about 50km south of Fort McMurray, were "under extreme threat" as the flames spread to the southeast.

More than 80,000 people have already been evacuated as the out-of-control blaze has burned down whole neighbourhoods of Fort McMurray and forced a precautionary shutdown of some oil production, driving up global oil prices.

Three days after the residents were ordered to leave, firefighters were still battling to protect homes, businesses and other structures from the flames.

More than 1,600 structures, including hundreds of homes, have been destroyed [CBC News/Handout via Reuters/Terry Reith]

The Alberta government, which declared a state of emergency on Thursday, said more than 1,100 firefighters, 145 helicopters, 138 pieces of heavy equipment and 22 air tankers were fighting a total of 49 wildfires, with seven considered out of control. 


READ MORE: Wildfire forces evacuation of Canada's For McMurray


There have been no injuries or deaths so far, but at least one vehicle crash with fatalities on the evacuation route was reported.

Notley said financial support will be provided to Albertans and that cash cards may be made available for evacuated residents.

More than 1,600 structures, including hundreds of homes, have been destroyed.

The fire has also destroyed nearly a third of the country's daily crude capacity. At least 64,000 barrels of crude output is offline as a result of the fire, according to Reuters news agency.

Although the cause of the fire is unknown, officials said tinder-dry brush, low humidity and hot, gusting winds left crews unable to stop the massive conflagration.

The blaze, which erupted on Sunday, was contained south of Fort McMurray until Monday. However, the inferno quickly expanded, forcing the city's evacuation.

A government worker surveys the damage on a street in Fort McMurray [Alberta RCMP/Reuters]

Source: Agencies