Carbon monoxide poisoning at a motel in Canada sent 46 people to the hospital, including 15 in critical condition, city officials said.

The fire department responded to an alarm at Super 8 Motel in Winnipeg, Manitoba, on Tuesday morning after carbon monoxide gas was detected in the building.

At the scene, fire crews evacuated 52 people -- a majority of whom were hospitalized -- and one dog, the city tweeted Tuesday. Winnipeg Animal Services provided care for the dog.

"Today's incident at a Winnipeg hotel was not a gas leak. It was a carbon monoxide poisoning," Manitoba Hydro tweeted. "CO is produced by the incomplete combustion/ventilation of gas stoves, heating boilers, furnaces, propane barbecues, gas-powered water heaters & clothes dryers."

The gas company said while natural gas has a rotten egg smell that helps with detection, carbon monoxide is odorless. For it to be detected, one needs a carbon monoxide alarm.

The initial symptoms of carbon monoxide poisoning are flu-like, but without a fever. They may include dull headache, weakness, dizziness and nausea. High-level poisoning can result in vomiting, shortness of breath, confusion, blurred vision and loss of consciousness.

When carbon monoxide levels are higher and develop more rapidly -- for example, from generators in residential spaces -- mental confusion can set in rapidly. Victims may lose muscle control without being aware of the flu-like symptoms and will probably succumb to poisoning if they are not rescued.