The firefighters were already in the building, arriving within minutes of our call; the police also came a few minutes later. In all, about two dozen firefighters walked up and down our building trying to locate the source of the smoky smell, which they attributed to either a "burning pot on the stove or some paper."
After about 45 minutes of searching, they had no luck in finding the source. We returned to our apartment at about 4:30 am, and there remains a faint smoke smell: I would have been happier if they had found the source. The youngest and my wife went back to sleep; the oldest couldn't and is now watching TV. And I writing.
We thank the Toronto firefighters for their professionalism. I am still a little shaken, recalling memories of a fire that destroyed our residence when I was 12. But we are all well, although tired.