Got woke up by this one this morning.
Then. Oops. Our bad.
That's quite a highly populated area and I'm sure there was quite a few worried people. Turns out it was a training exercise not meant for public release.
Also had no idea that if you lived within 10km of a nuclear plant the government sends you out a fresh stock of potassium iodide every six months.
https://www.cbc.ca/news/canada/toron...tion-1.5424115