As many as 100,000 people could be forced from their homes by heavy flooding in western Canada, Calgary city officials said, while mudslides forced the closure of the Trans-Canada Highway around the mountain resort towns of Banff and Canmore, Belfast Telegraph said.

Torrential rains and widespread flooding throughout southern Alberta have washed out roads and bridges, left at least one person missing and caused cars, sofas and fridges to float away. Communities just south of Calgary were hit hardest.

Officials said the evacuation would take place in stages over the next few days. The province reported that 12 communities were under states of emergency.

One woman who was stranded on top of a trailer is missing after it was swept away, air ambulance spokesman Cam Heke said.

Motorists who were trapped overnight by water spilling over Canada's main western highway had to be rescued by helicopter, Town of Canmore spokeswoman Sally Caudill said.

In High River, Mounties asked people with motorboats to help rescue at least a dozen stranded homeowners.

Environment Canada issued a rainfall warning for the affected areas, estimating as much as 3.9in more rain could fall in the next two days.