09/25/2014 01:53 EDT | Updated 11/25/2014 05:59 EST

Toronto City Hall evacuated as transformer fire reported

Toronto City Hall has been evacuated, the building's power is out and police say the roads surrounding it have been closed as a result of a transformer fire on Thursday afternoon.

Officials are calling it a two-alarm fire. Paramedics say three patients were taken to a local hospital with minor smoke inhalation.

Toronto firefighters and hydro workers are on scene. The cause of the transformer fire is not immediately known.

Firefighters say the hydro vault has been "de-energized."

Coun. Kristyn Wong-Tam tweeted hearing "a thunderous boom" before the building was evacuated.

More to come