CALGARY, Alberta — Flooding forced the western Canadian city of Calgary to order the evacuation of its entire downtown Friday, as the waters reached the 10th row of the city’s hockey arena.

Overflowing rivers washed out roads and bridges, soaked homes and turned streets into dirt-brown waterways around southern Alberta. Police say as many as four people might have died.

About 350,000 people work in downtown Calgary on a typical day.

However, officials said very few people need to be moved out, since many heeded warnings and did not go to work Friday.

Twenty-five neighborhoods in the city, with an estimated population of 75,000, have already been evacuated due to floodwaters in Calgary, a city of more than a million people.

Outside the city, the Royal Canadian Mounted Police said two men were seen floating lifeless in the Highwood River near the hard-hit community of High River on Thursday, but no bodies have been found. They also say a woman who was swept away with her camper has not been located. And it wasn’t clear whether a man who was seen falling out of a canoe in the High River area was able to climb back in.

In downtown Calgary, water was inundating homes and businesses in the shadow of skyscrapers.

Water has swamped cars and train tracks. The city said the home rink of the National Hockey League’s Calgary Flames flooded and the water inside was 10 rows deep.

“I think that really paints a very clear picture of what kinds of volumes of water we are dealing with,” said Trevor Daroux, the city’s deputy police chief.

About 1,500 have gone to emergency shelters while the rest have found shelter with family or friends, Mayor Naheed Nenshi said.

The mayor suggested that levels on the Bow River — which, in Nenshi’s words, looked like an ocean — would remain steady for the rest of the day as long as conditions didn’t change.

Police urged people to stay away from downtown and not go to work.