Rémi Perry, Montreal Fire Service's chief operating officer, said the fire started in the basement at 306 Spring Garden Street shortly after 4 a.m.
The fire quickly spread to the first floor, he said.
"Our firemen are still on the scene. The fire is under control," said Perry. "We don't have the cause of the fire because our investigator cannot get in right now."
One person was taken to hospital for smoke inhalation.
Perry said the cold weather is making the job difficult for firefighters themselves and for their equipment. He said frozen hoses and mechanical problems often arise in these conditions.
He said electrical surges and fireplaces are the main causes of fires this time of year.Suggest a correction