India, Aug. 12 -- A deadly wildfire in western Canada that has forced some 20,000 people to flee grew overnight even without strong winds, challenging efforts to contain it and fully assess the damage, authorities said.

About 100 firefighters from Mexico were on the way to help fight the blaze, which has destroyed homes and other properties near Okanagan Lake in British Columbia. The fire has killed an 80-year-old woman and burned toward Summerland, a community of about 12,000 people roughly 300 km east of Vancouver.

The fire showed "quite significant growth" in some areas overnight, even without strong winds, said Cliff Chapman, director of provincial operations for the British Columbia Wildfire Service. He added that crews were workin...