TORONTO (Reuters) - Authorities in Canada's wildfire-ravaged energy heartland have lifted evacuation orders on Suncor Energy Inc SU.TO and Syncrude oil sites after rain and cold weather helped dampen the flames.

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Municipal authorities in the oil town of Fort McMurray lifted the mandatory evacuation orders on Suncor’s base plant and Syncrude’s Mildred Lake facility, as well as nearby camps that house oil workers, late on Friday.

Suncor said on Facebook that a limited number of staff will be back at some of its sites on Monday at the earliest and that all will return “in a phased manner over the next few weeks,” but it is unclear when it will restart production. A Suncor spokeswoman said on Saturday that the plans posted on Facebook had not changed.

Syncrude, majority-owned by Suncor, is still monitoring the situation and does not yet have a timeline for restarting production, although it does have skeleton crews at its sites, a spokesman said.

Fort McMurray itself still sits largely empty, after its entire population of nearly 90,000 was evacuated in the northern Alberta fire that has blackened more than 500,000 hectares (1.2 million acres) since it began earlier this month.

The fire also triggered a prolonged shutdown that has cut Canadian oil output by a million barrels a day.

The blaze forced the evacuation of Suncor and Syncrude facilities and nearby camps after it jumped a critical firebreak late Monday, moving north of Fort McMurray into oil sand camp areas. Some 8,000 workers were evacuated.

Producers have since signaled a gradual increase in operations.

The fire has “waned” since Friday, though it remains the same size Saturday morning, said Alberta wildfire information officer Laura Stewart.

She said the fire has not had additional impact on oil facilities and is not expected to grow in size over the weekend.

The Regional Municipality of Wood Buffalo, which oversees Fort McMurray, tweeted the area received 2 mm (0.079 inches) of rain overnight.

Some of the evacuees from Fort McMurray may be allowed to return as soon as June 1, if air quality improves and other safety conditions are met.