Forest fires in Canada's western province of British Columbia intensified further on Saturday, doubling the number of people under an evacuation order to 35,000 from a day earlier, as authorities warned of difficult days ahead.

The province declared a state of emergency on Friday to access temporary authoritative powers to tackle fire-related risks, as out-of-control fires ripped through interior British Columbia, destroying scores of properties and partially shutting down some sections of a key transit route between the Pacific coast and the rest of western Canada.

"The current situation is grim," Premier Daniel Eby told reporters on Saturday, saying some 35,000 people are under an evacuation order, and a further 30,000 were under evacuation alert.