(CNN) -- Rain-swollen rivers burst from their banks in southern Alberta, Canada, ripping out roads, cutting off communities and forcing about 75,000 people out of their homes in Calgary alone.

"In my lifetime, I have never seen flooding like this," Calgary Mayor Naheed Nenshi told CNN on Friday.

Authorities said they had completed a challenging overnight evacuation of 25 neighborhoods without any injuries or deaths.

But portions of the city of 1 million people -- famous for the annual Calgary Stampede rodeo -- were covered in deep water Friday, including parts of downtown. Nenshi asked people to stay away, in part to keep roads clear for emergency workers.

They also asked people to limit telephone use out of concern that unnecessary phone calls could overwhelm the system and diminish the ability of emergency responders to do their jobs.

Power was out in portions of the city, and some shelters were filled to capacity, Calgary officials said Friday. Schools were closed in the city.

The emergency in Calgary follows devastating flooding in rural areas of southern Alberta, hitting towns such as High River and Canmore hard. Authorities declared a state of emergency in several cities, including the mountain town of Canmore, where on Thursday, raging waters tore out a portion of the Trans-Canada Highway.

"Like everything, everything, is destroyed there -- our homes, like everything," Alberta resident Melanie Atkinson, who lost her home in the flooding, told Canadian broadcaster CBC.

Rescue crews used heavy construction equipment to rescue people from homes and businesses Thursday in High River, the network reported.

Canada's military was pitching in with helicopters and other assets to help local officials with rescue and evacuation efforts, Prime Minister Stephen Harper said.

"Our thoughts and prayers are with those families who have been affected by the serious flooding in Calgary and Southern Alberta," Harper said, adding that the federal government would provide "any and all possible assistance."

No deaths or injuries have been reported.

In Calgary, officials closed many bridges as water levels became dangerously high. The city zoo closed and began moving animals to safer locations.

Nenshi said one of the city's two rivers -- the Elbow -- had crested, but it appeared that the other -- the Bow -- was still rising. Emergency officials have said they expect the river to remain high through at least Saturday.

Calgary police said they were patrolling evacuated areas to ensure that vacant homes and businesses would remain as safe as possible.

The flooding was caused by a slow-moving storm that dumped 154 millimeters (more than 6 inches) of rain on the region from Wednesday to Thursday, CNN meteorologist Sherri Pugh said. As much as another inch of rain is possible northwest of Calgary on Friday, and yet another front is expected Monday, bringing the threat of yet more rain.

Calgary, near the Canadian Rocky Mountains, is perhaps best known for its rodeo, held each July. More than 1.4 million people attended last year, organizers say.

Calgary authorities are using the park where the stampede is held as a staging area for flood response efforts. It will probably see some flooding, organizers said early Friday.

CNN's Joe Sutton and Jake Carpenter contributed to this report.

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