MONTREAL -- A fire that broke out on the balcony of Margaret Trudeau’s Montreal apartment was started by a propane heater, the Montreal fire department has confirmed.

Prime Minister Justin Trudeau's mother was taken to hospital late Monday night to be treated for smoke inhalation and possible burns after being exposed to the fire.

Trudeau is recovering well, said fire department section chief Matthew Griffith.

Griffith confirmed that an investigation into the cause of the fire has been completed and that it has been deemed accidental.

Griffith said the propane heater on Trudeau’s fifth-floor terrace came into close contact with a combustible material, sparking the blaze.

About 70 firefighters were called to the scene on Doctor-Penfield Avenue near the Atwater Avenue intersection around 11:25 p.m. Monday night.

The fire was contained to one apartment unit. Three other families were also forced to evacuate the building, but no one else was injured.