CALGARY - A powerful windstorm in Calgary that smashed windows in a highrise office tower has prompted officials to close traffic in the city's downtown, and issue a warning to stay indoors.

"Right now, there's just so much stuff falling off buildings that we're struggling to keep up with calls," said Det. Dean Vegso of the Calgary Police.

Environment Canada says gusts of over 100 kilometres per hour have been reported in some parts of southern Alberta on Sunday afternoon.

The province's emergency alert system has broadcast a warning on radio stations that residents should stay away from windows, and should watch out for flying debris.

The City of Calgary says several large windows were ripped out of the TD Square office building.

A vehicle was damaged but no one was hurt.

Several crossing arms along Calgary's light rail system were also broken off by the strong wind.

Trees have also been blown onto roadways, and RCMP are advising that large vehicles should stay off Highway 2 south of Calgary between Nanton and Fort Macleod.

In High River, south of Calgary, residents were told to leave an apartment building after municipal officials said a fire wall had separated from the building.

"It's a lot more severe out in the country where there isn't anything to block the winds when it's coming across the fields," said Jillian Millar, who drove south from Calgary on Sunday afternoon with her husband to pick up their daughter from a party.

"We didn't realize it was as bad as it was when we left the house," she added.

Millar says farm animals were seeking shelter behind whatever they could find. She said she saw horses huddled beside a parked school bus.

Power was knocked out briefly to a number of her neighbours' homes in Calgary.

Despite police closing traffic to Calgary's downtown, the owner of a Calgary sports bar in the city's core said he still made it to work, and he said football fans were still getting in to watch the Grey Cup on his television screens.

Charlie Mendelman said he saw the police roadblocks on his way into downtown, but was able to find a way around them.

"I was born and raised in Calgary, so I know the streets really well," Mendelman said.

Police said it was fortunate the damage downtown happened on a Sunday.

"There would be a lot more people walking if it was a weekday," Vegso said.