By Nia Williams and Scott Haggett
CALGARY, Alberta (Reuters) - Firefighters battled wildfires in northern Alberta, Canada's biggest crude-producing region, for a sixth day on Thursday, with two blazes near oil sands facilities still out of control.
The wildfires have forced producers in the Western Canadian province, the largest source of U.S. crude imports, to shut in 233,000 barrels per day of crude production, around 10 percent of total oil sands output.
The biggest fire, on the Canadian military's Cold Lake Air Weapons Range, had grown in size to 20,000 hectares (49,000 acres) from 17,000 hectares on Wednesday.
That blaze has forced Cenovus Energy Inc and Canadian Natural Resources Ltd to shut down production and evacuate staff from their Foster Creek and Primrose oil sands projects.
Janelle Lane, a wildfire information officer at the Alberta government, said the fire had advanced to roughly 15 kilometers (9.3 miles) away from Cenovus's Foster Creek site.
Although the two oil sands facilities are not threatened directly by the wildfire, it has closed the only access road to the projects. Both Cenovus and Canadian Natural said the status of their operations was unchanged on Thursday.
Rich Kruger, chief executive of Imperial Oil Ltd, told reporters on Thursday the blaze was just six kilometers away from one of the company's wells but there was as yet little risk to Imperial's extensive operations in the region.
"We're monitoring it very carefully," he said. "It's had a minimal impact on our operations to date but as winds change, I find myself praying for rain more often than I used to."
A separate wildfire north of the hamlet of Conklin forced MEG Energy to evacuate nonessential staff and halt planned maintenance work at its Christina Lake oil sands project earlier in the week. That blaze has grown to 3,300 hectares and was still classed as out of control, Lane said.
A number of other oil sands projects across the province have evacuated staff and slowed operations due to other fires.
Firefighters made some progress in tackling blazes elsewhere in Alberta, with the number of fires burning dropping to 42 on Thursday morning from 63 on Wednesday afternoon. Of those, 10 were uncontrolled.
Lane said a low pressure system moving east from British Columbia had already brought much-needed rain to some parts of the province, with more precipitation expected over the weekend.
(Editing by Peter Galloway)