A small fire that injured one person at Old City Hall on Friday afternoon was likely deliberately set, an official tells CP24.

Firefighters were called to the national historic site on Queen Street West, just west of Yonge Street, when someone reported a burning rag in a first-floor washroom at about 12:45 p.m.

After smoke triggered the fire alarms, people were forced to leave the 114-year-old building, which houses a provincial courthouse, and court sessions were put on hold.

A court security officer was treated at the scene for smoke inhalation, said Toronto Fire Services Capt. David Eckerman.

The building sustained minimal smoke damage, Eckerman told CP24 as fire crews ventilated the interior.

With files from CP24 reporter Katie Simpson.

@ChrisKitching is on Twitter. For instant breaking news, follow @CP24 on Twitter.