Work to bring about 94,000 evacuees back to fire-ravaged Fort McMurray has slowed, under a blanket of smoke so toxic it surpasses provincial measurements.

Alberta uses a one to 10 scale to measure air quality, with one being the lowest risk and 10 considered the highest risk.

Air quality in the Fort McMurray area on Monday morning was 38.

mask

People working in Fort McMurray are encouraged to wear N95 masks, like the one pictured in this file photo. (Nathan Denette/Canadian Press)

In a news conference at the beginning of the day, Premier Rachel Notley urged members of the public who are not already in Fort McMurray to stay away for now.

"Alberta Health Services has recommended that members of the public who had been previously arranging to return to the area under various requests, that they not return until those conditions improve," she said.

Her office did not clarify whether the warning applied to the hundreds of oil workers who had planned to return to camps north of Fort McMurray this week.

But around 4 p.m. Monday, an order went out to evacuate several camps just north of the city, including the Noralta Lodge. That evacuation included some oil workers who had returned to area just one day earlier. 

Delays and new dangers

Plans to bring in more workers to help with re-entry have also been suspended, as has the vehicle retrieval program announced over the weekend.

Emergency personnel are limiting the working hours of their staff in the town site where possible, and making sure everyone is fitted with proper face masks.

"It is clear that this is something that could potentially delay recovery work and the return to the community," Notley said.

smoke

Heavy yellow smoke obscures a road sign at the north end of Fort McMurray, in this photo taken by a CBC listener Monday morning. (Supplied )

On Monday, the fire was an estimated 284,214 hectares in size. Bad air quality was expected to continue for 24 to 48 hours.

And amid that smoke, fire crews must fight new battles.

The toughest one may be to hold flames back from an Enbridge tank farm near Anzac. Officials said the fire was one kilometre from there, and said bulldozers and specialized industrial firefighters were working "very hard" to hold that boundary.

When can they go home?

RE-ENTRY NUMBERS

19,280 structures have been assessed for damage

400 staff are working to get hospital back online

300 ATCO workers are restoring services

32 km of fencing ordered to secure hazardous areas

70,000 views on new Fort McMurray satellite maps

27,736 debit cards distributed, worth more than $60 million

Gas service restored to about 50 per cent of the city

Electricity restored to most of the city

Crews are also watching hotspots surrounding Fort McMurray, in extreme fire conditions Notley described as just as bad as the day of the mass-evacuation.

"Any one of them could flare up when the wind changes," she said.

Strong southwest winds and dry conditions had senior wildfire manager Chad Morrison predicting flare ups and fire growth in the fire's northern and northwestern flanks.  

"It's still not safe for folks to be back there," he said.

Officials announced over the weekend they were ready to name a re-entry date for residents within the next week and a half. But the premier said Monday she's not ready to release a specific plan.

"I know they desperately want a calendar that they can plan their lives around," she said.

"At the same time, giving them deadlines, throwing out potential scenarios when we don't have all the information at our disposal, would be irresponsible."