The incident occurred at a Super 8 motel in the Prairie-region city.

"This was a major serious incident," Alex Forrest, president of the United Fire Fighters of Winnipeg, told CBC News.

He said carbon monoxide readings at the motel came in at 385 parts per million -- well above the 10 to 20 parts per million at which carbon monoxide levels become dangerous.

According to the CBC, Manitoba Hydro, the province's energy utility that provides electricity and natural gas services, said it had turned off the leak, which did not come from gas.

They did not yet know the source.