CALGARY, Alberta (Reuters) - A massive wildfire burning around the oil sands hub of Fort McMurray was growing and moving rapidly north late on Monday (May 16), forcing firefighters to shift their focus to protecting major oil sand facilities north of the city, officials said.

The sudden movement of the fire prompted the evacuation of some 4,000 people from work camps outside Fort McMurray, with all northbound traffic once again cut off at the city, the Regional Municipality of Wood Buffalo said.

Suncor Energy Inc and Syncrude Canada confirmed they had evacuated workers from the affected area. Their major facilities were under a precautionary notice with the fire still some 15 to 20 kms away, officials said.

A dozen work camps south of the major projects faced mandatory evacuation notices. "The urgency we're looking at is with regards to the oil gas infrastructure," Scott Long, executive director of the Alberta Emergency Management Agency, told reporters in Edmonton, adding Fort McMurray itself appeared to be safe for now.

The entire population of Fort McMurray, about 90,000 people, was forced to flee nearly two weeks ago as the uncontrolled wildfire raged through some neighborhoods and destroyed about 15 per cent of structures.

On Monday, the blaze continued to burn uncontrolled, now covering 285,000 hectares, officials said. By Monday evening it was moving 30 to 40 metres every minute and had jumped a critical firebreak north of the city to push into the oil sand camp areas.

"When you have this type of extreme fire behaviour, it doesn't matter what tankers you put in front of it, or how many helicopters, Mother Nature is going to continue to move that fire forward," wildfire manager Chad Morrison said.

Morrison said the blaze was expected to slow into the evening and that it was unclear if it would reach the major oil sand facilities, though responders were preparing for that eventuality.

A Suncor spokeswoman said 120 people were evacuated from its MacKay River plant and camps as a precautionary measure Monday afternoon, adding the facilities were not at risk from the fire.

Syncrude, a joint venture among numerous energy companies operating in the region, said on Twitter that it was relocating its workers to safety.

The fire also threatened Enbridge Inc's Cheecham crude oil tank farm south of Fort McMurray. The blaze, about 1 km away from the tank farm, was under control with the wind cooperating as the company's industrial firefighters tackled the fire, officials said earlier in the day.

Enbridge said a firebreak around the terminal was being widened and that crews were assessing other fire suppression tactics like spraying down facilities. It said some pipelines in and out of the terminal were operating, and the situation was being monitored.

Roughly a million barrels per day of oil sands crude production was shut in as a precaution and because of disruptions to regional pipelines, and much of that production remains offline.

CITY SAFE, FOR NOW

Firefighters have managed to protect much of Fort McMurray but evacuated residents are still not allowed to return to their homes, partly because of hotspots around the community.

By Monday evening, the wildfire was again burning next to the neighborhood of Timberlea, with some 150 to 200 firefighters working to keep the burn from spreading back into the community.

Alberta Premier Rachel Notley said there was still no timeline on when residents could return but she hoped to have more information by the end of the week.

Officials said the air quality in the city had deteriorated, with the air quality health index, usually measured on a scale of 1-10, at 38 on Monday.

"This has delayed the re-entry of additional response personnel as well as vehicle retrieval efforts," Notley said."It is clear that this is something that could potentially delay recovery work and the return to the community."

Canadian Finance Minister Bill Morneau told CBC News the Fort McMurray fire would be a challenge to the economy as well as a human challenge, but he had no price tag yet on how much the disaster would cost the federal government.

"We're obviously going to stand shoulder to shoulder with the people in Fort McMurray and rebuild the city," he said.