Environment Canada confirms that a low intensity tornado struck near Tottenham, Ont., on Tuesday afternoon.
The agency was also checking reports late Tuesday that another tornado may have struck near Hawkesbury, Ont., on the Quebec border.
Environment Canada says its survey teams have rated the Tottenham tornado as an EF-1 with maximum winds between 135 and 175 kilometres per hour.
Watch an eyewitnesses' video of the tornado.
WARNING: there is graphic language in this video
The agency's preliminary investigation suggests the tornado had a path length of at least 10 kilometres and damaged at least one house. A riding stable was also damaged, and two horses were hurt, but there were no reports of any other injuries.
Some roads in the area were closed due to the severe weather and residents were asked to keep an eye out for downed trees and hydro wires.
Environment Canada says a further investigation will be conducted Wednesday in the area about 50 kilometres north of Toronto.
The tornado comes a week after an EF-2 tornado hit Angus, about 35 kilometres north of Tottenham, injuring three people and damaging more than 100 homes.