Municipal authorities in Alberta said they were permitting a phased re-entry for some energy company employees as the wildfire threat evolves.

Around 1 million barrels per day worth of Canadian oil production was impacted by wildfires raging through parts of Alberta, home to the country's oil sands operations, since early May. The provincial government said fires remain out of control, with more than 1,900 square miles burned.

A series of evacuation orders were issued over the past month, though the provincial government said during the weekend that voluntary re-entries were permitted. The municipality of Wood Buffalo, one of the hardest hit, confirmed some of those plans to re-occupy some oil sands installations would get under way immediately.

"The regional emergency operations center has endorsed Alberta Agriculture and Forestry's recommendation to allow a phased re-entry," the provincial government said.

Alberta's provincial government met in mid-May with energy company executives to discuss the threats to the industry posed by fires in the region. Few of the nation's oil sands installations were damaged by the fires, though operations and deliveries were curbed.

Some mandatory evacuation orders for oil sands installations were lifted last week. Local and provincial officials said they're calling for voluntary resettlement for Fort McMurray residents starting June 1, provided wildfire conditions aren't prohibitive.

For residents, natural gas service and electricity has been restored for more than 70 percent of the undamaged structures in Fort McMurray.