Suncor, Canada's second-largest oil producer, said it was keeping only essential workers at the facility, which lies roughly 100 kilometres northeast of the oil sands hub of Fort McMurray.
The company declined to comment on whether Firebag production had been affected.
"An emergency-response team is monitoring the situation closely and prepared to take further action if necessary," a Suncor spokesperson said in a statement.
"There is no risk to our other operations or the Firebag airport at this time."
Alberta's Minister of Forestry and Parks Todd Loewen said Firebag had been shut down on Wednesday night out of caution.
There are more than 60 fires across Alberta and officials have rated the danger in the province's north as very high to extreme, he added.
Canada is the world's fourth-largest oil producer and more than two-thirds of its 5 million bpd of crude comes from Alberta's oil sands.
Imperial Oil (IMO.TO), whose Kearl oil sands mine is about 20 kilometres north of Firebag, and Cenovus Energy (CVE.TO), whose Sunrise facility is to the south, said their operations had been not affected at present.
"We are closely monitoring the evolving wildfire activity across northern Alberta, including near our Sunrise facility," Cenovus said in a statement.
The blaze threatening Suncor's site is part of the out-of-control Firebag Complex of wildfires, which is comprised of several new lightning-caused fires, according to Alberta's provincial wildfire agency.
Weather forecasts show an extended period of hot weather will settle over Western Canada in the coming days, with temperatures expected to exceed 30 degrees Celsius (86 degrees Fahrenheit) by next week.
So far the wildfire season in Canada has been much quieter than last year, when more than 6,600 fires scorched a record-breaking 15 million hectares, an area roughly seven times the annual average.
But large swathes of western Canada are still abnormally dry due to ongoing drought and wildfire season tends to peak in July and August.
