A catastrophic wildfire that has forced all 88,000 residents to flee Fort McMurray in Alberta, Canada exploded tenfold in size on Thursday, cutting off evacuees in camps north of the city and putting communities to the south in extreme danger.

The out-of-control blaze has burned down whole neighborhoods of Fort McMurray in Canada's energy heartland and forced a precautionary shutdown of some oil production, driving up global oil prices.

Three days after the residents were ordered to leave Fort McMurray, 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.

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

"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 warned that the communities of Anzac and Gregoire Lake Estates about 50 km (31 miles) south of Fort McMurray were "under extreme threat," late on Thursday, as the flames spread to the southeast.

Fire has intermittently blocked the only route south toward major cities, so thousands of evacuees fled north toward oil camps and a few small settlements. On Thursday, frustration for those stranded up north was growing, with some venting on social media sites, demanding answers.

One twitter user posted a message saying, "NO ONE IS TELLING US ANYTHING!! We're just sitting in a camp praying to get out!! Give us answers!!! Please."

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

Officials said with the fire moving to the south east, they are also hoping to be able to begin a ground evacuation from the north on Friday morning.

Although the cause of the fire was 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, grew from 18,500 acres (7,500 hectares) on Wednesday to some 210,000 acres (85,000 hectares) on Thursday, an area roughly 10 times the size of Manhattan.

GHOST TOWN

Hundreds filled a community center on Thursday morning in Lac La Biche, a community about 170 miles (290 km) south of Fort McMurray. Many were second-round evacuees who were ordered to relocate from temporary refuges closer to Fort McMurray on Wednesday night as the flames grew.

Other people bunked down in a Lac La Biche high school, its gym converted to a used-clothing station for the evacuees.

Kirby Abo, who came from Fort McMurray with his wife and three children, said he worried that his job in a recycling depot may no longer exist when he returns home.

"I think it's going to be a ghost town for quite a while," he said.

Fort McMurray's mayor, who is stranded to the north, said in a television interview the city faces a long road to recovery and "what comes next is absolutely daunting, but not insurmountable."

The winds gave the city a brief reprieve on Thursday by driving the fire to the southeast, away from populated areas. But officials warned that the unpredictable weather could quickly shift again.

At least 680,000 barrels per day of crude output is offline, according to Reuters calculations, or roughly 20 percent of Canada's crude production. The outage is expected to climb as major players in the region cut production. 

Authorities said there had been no known casualties from the blaze itself, but fatalities were reported in at least one vehicle crash along the evacuation route.

Notley said a water tanker plane slid off the runway in another part of the province. Police said the two pilots survived, but were taken to hospital as a precaution.