A wildfire burning in Jasper National Park's Chetamon Mountain is now estimated to cover an area of around 6,000 hectares, Parks Canada said Monday evening.

A lightning strike on September 1 started a fire that grew from 400 to 1500 hectares by Sunday, September 3.

Power went out again on Monday morning after being restored on Sunday evening. Jasper Mayor Richard Ireland warned this outage could be for an extended period of time. 

The message to residents and visitors is that in the face of uncertainty they should be prepared, as they can not say how long 'extended' may be. 

As of Sunday, there were eight helicopters flying over the fire to drop water on the flames, along with over 70 Parks Canada firefighters and personnel.

In addition, there are other pilots and contractors working to prevent the fire from spreading to high-risk areas, the agency said.

The fire spread to the Atco, Trans Mountain, and Canadian National Railway lines, officials said.

Parks Canada has closed Snaring and Celestine Lake Roads and surrounding areas, including nearby campgrounds, to ensure public safety during fire operations.

The agency also restricted aircraft take off and landing at the Jasper air strip, citing public safety.