FORT MCMURRAY, Alberta (AP) — A raging wildfire emptied Canada's main oil sands city, destroying entire neighborhoods of Fort McMurray, Alberta, where officials warned Wednesday that all efforts to suppress the fire have failed.

About 88,000 residents successfully evacuated as flames moved into the city surrounded by wilderness in the heart of Canada's oil sands. No injuries have been reported. Alberta Premier Rachel Notley said there is significant destruction and estimated 1,600 structures have been destroyed or damaged.

Unseasonably hot temperatures combined with dry conditions have transformed the boreal forest in much of Alberta into a tinder box. The wildfire threat ranged from very high to extreme in different areas.

An overnight update from the Regional Municipality of Wood Buffalo said the Beacon Hill suburb in the south end has suffered the most damage from flames with 80 percent of the homes lost. A dozen trailers on one street in the neighborhood of Timberlea have gone up in flames, with serious losses are reported in the Abasand and Waterways suburbs. Some homes have been lost in four other neighborhoods.

"This is a nasty and dirty fire," Fire Chief Darby Allen said.

Official estimated the fire at 7,500 hectares (18,500 acres) and said they expect it to be worse Wednesday as strong winds and high temperatures "will again create explosive conditions."

Allen earlier said parts of wooded areas of the city are still burning but no structures were currently on fire. Firefighters were working to protect critical infrastructure, including the only bridge across the Athabasca River and Highway 63, the only major route to the city in or out. The downtown remains largely untouched.

"It's a possibility that we may lose a large portion of the town," said Scott Long of the Alberta Emergency Management Agency.

Forestry manager Bernie Schmitte said there was still danger from "very high temperatures, low relative humidities and some strong winds."

Canadian Public Safety Minister Ralph Goodale said in a statement Wednesday he is watching the situation with "great concern" and said "situation is fluid and evolving rapidly." He noted the federal government is monitoring the situation carefully, including the military.

Defense Minister Harjit Sajjan, in a conference call from Germany early Wednesday, confirmed a formal request for assistance has been received from the Alberta government. What form that will take — at least on the military side — is still being determined and they are expecting to hear soon about the kind of equipment and personnel required.

"We're making all assets available," he said.

Alberta Premier Rachel Notley called it the biggest evacuation in the history of the province. Canadian Prime Minister Justin Trudeau while the full extent of the damage isn't yet known he called it "absolutely devastating" and said there's a loss on a scale that's hard to imagine. He said his thoughts are with Alberta and said he's offered the premier the federal government's full support. He encouraged Canadians to support friends and donate to the Red Cross.

"We will be there for them," Trudeau said, adding that the military aircraft are being mobilized to help fight the blaze.

The Alberta oil sands are the third largest reserves of oil in the world behind Saudi Arabia and Venezuela. Most oil sands projects are well north of the community, while the worst of the flames were on the city's south side. Allen said he's not aware of any threat to oil facilities but called the fire a "moving animal."

The Regional Municipality of Wood earlier said evacuees who are north of Fort McMurray should stay north because they are safe. Notley said about 10,000 evacuees moved north.

Suncor, the largest oil sands operator, said it is reducing production at its regional facility - about 15 miles north of the city - so as "to allow employees and their families to get to safety."

Resident Breanna Schmidt said evacuating almost felt like "an apocalypse."

"We had to literally drive through smoke and fire, vehicles littered all over the sides of the road, and we had to drive as fast as we could and breathe as little as we could because the smoke was so intense and we could feel the heat from inside the vehicle," she said.

Former National Hockey League player Doug Sulliman said he could see from his apartment balcony that both sides of the highway south were engulfed in flames and estimated hundreds of homes in Beacon Hill suburb over the hill were destroyed. "You could hear the pop, pop, pop because of the propane tanks. The fire was just consuming these houses. It just destroyed the whole community," he said.

He decided the best place to stay was the apartment, but he was forced out three hours later.

"I woke up just in time," he said in a phone interview. "Smoke had come into the apartment, but not bad. When I opened the door to the hallway it was burning my eyes and when I went outside it was burning my throat."

He said the highway opened and it was bumper to bumper and said there were many cars on the side of the road because service stations were out of fuel. He said RV campsites were destroyed.

"There was a Shell gas station that blew up and a Denny's next door. There was nothing but the foundation and it was still smoldering in flames," he said.

The blaze had burned since Sunday and seemed on its way to being neutralized Tuesday morning, but it overwhelmed firefighters when winds shifted quickly and drastically mid-afternoon Tuesday. Pictures and video on social media depicted a hellish scene of fire jumping roads and burning debris pitched into the paths of cars as frantic residents, lined up bumper to bumper, scrambled and fumbled to find their way through the thick gray haze.

Oil sands work camps were being pressed into service to house evacuees.

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Associated Press reporter Rob Gillies in Toronto contributed to this report.