Wildfires in northern Alberta prompted some energy and transportation companies to temporarily shut down operations Monday.

Fires in and around Slave Lake on Sunday have resulted in the mandatory evacuation of the town after the destruction of hundreds of homes, churches and businesses.

Calgary-based Penn West Petroleum said it has shut in 25,000 to 30,000 barrels a day of heavy oil production in north-central Alberta and suspending drilling in the region.

"We are monitoring the spread of the fire and the potential for additional production shut-ins," the company said in a release.

Employees in the area have been removed and all are safe, although some have lost homes.

Penn West's operations have also been affected by flooding in Manitoba and Saskatchewan, curtailing the company's total daily production by about 20 per cent or 35,000 to 40,000 barrels of oil equivalent.

Cenovus Energy, also based in Calgary, was preparing to suspend output from its Pelican Lake heavy oil operations, 90 kilometres northeast of Slave Lake, which produce 22,000 barrels of oil per day.

Sixty-five employees work at the project, and they and their families are not in danger, the company said.

But the company is unable to transport oil from the facility because of the closure on Sunday of the southern leg of the Plains All American pipeline from a terminal northwest of Slave Lake.

The northern leg had been shut down since April 29 after a break that spilled 28,000 barrels

Montreal-based Canadian National Railway also said it had halted service in the area around Slave Lake.

Canadian Natural Resources evacuates camps

Another Calgary firm, Canadian Natural Resources Ltd., said it had removed 1,300 personnel from two work camps as a result of a forest fire near its Horizon Oil Sands site.

The fire was about 150 metres from one of the camps, the Chelsea Lodge. The company said a fire barrier had been put in place and has been successful so far in diverting the forest fire away from the lodge and the oilsands site.

The fire has had no effect on any facilities at the Horizon operation, the company said.

Another Calgary-based oil producer, Exall Energy Corp., said it had shut production, 921 barrels of oil equivalent daily, at its Marten Mountain field.

During the evacuation, Exall said, its field operators were able to shut all of the company's Marten Mountain production for precautionary reasons.

Exall is assessing the effect the fires have had on its infrastructure and equipment.

"Aerial surveillance of the Marten Mountain area indicates that Exall's facilities and operations have not currently been impacted by the fires and are not at this time under threat from the fires," the company said in a release. "The fires currently appear to be south and east of Exall's Marten Mountain operations."

With files from The Canadian Press