A carbon monoxide leak at a hotel in Canada has sent 46 people to the hospital, with at least 15 of them in critical condition.

Emergency crews were called to the Super 8 hotel in Winnipeg, Manitoba, at around 10.20am Tuesday morning when an automatic alarm detected carbon monoxide gas, according to John Lane, chief of the Winnipeg Fire Paramedic Service.

A total of 52 people, including staff, and one dog were inside the hotel at the time.

Of the 46 taken to the hospital, 15 were listed in critical condition, five as unstable and five as stable.

All 46 people hospitalized in the carbon monoxide leak survived the incident and most have been released, a city health official said to CBC late Tuesday.

Authorities in Canada say a carbon monoxide leak at a Super 8 hotel in Winnipeg, Manitoba, has sent 46 people to the hospital, with at least 15 of them in critical condition (file photo)

Lane said 'none of the patients were requiring resuscitation, none of them were incubated or anything'.

Manitoba Hydro shut off gas to the building and is working to determine the cause of the leak.

They released a statement on Twitter explaining that the leak was carbon monoxide poisoning.

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

'Natural gas has a rotten egg smell (mercaptan) added to it so that it can be detected — carbon monoxide is odorless, which is why you need a CO alarm in your home and business,' it added.

When too much of the colorless, tasteless and odorless gas is in the air, the body replaces oxygen in red blood cells with carbon monoxide.

This can lead to serious tissue damage, or even death.

The highest carbon monoxide reading found in the hotel was 385 parts per million (PPM). Symptoms become noticeable at 70 ppm.

The hotel's carbon monoxide alarm went off just after 10am CT.

The motel's owner, Justin Schinkel, told CBC at the scene that at least one of his staff needed oxygen after the building was evacuated.

'It's a huge misfortune that this happened,' Motel owner Justin Schinkel told CBC at the scene.

'I'm super happy that the first responders got here as quickly as they did.'

Schinkel wasn't at the motel when the alarm sounded but rushed over as soon as he heard from a general manager.

He said the property recently had a fire inspection and has never had a gas leak.