About 4,000 workers from oil camps north of Canada's main oil sands city are being ordered to evacuate because of an approaching wildfire.

The Rural Municipality of Wood Buffalo calls it a precautionary evacuation of 12 camps.

Officials say the wildfire is moving 30 to 40 meters (33 to 44 yards) per minute and is expected to burn six kilometers (3.7 miles) in two hours.

Earlier Monday, officials warned the air quality in the Fort McMurray area was dangerously poor.

Alberta Premier Rachel Notley said the air quality health index is normally one to 10, with 10 being the worst, but the reading this morning was at 38.

It's the same wildfire that ignited two weeks ago, forcing more than 80,000 residents to evacuate and destroying more than 2,400 structures in Fort McMurray.