The fire erupted overnight yesterday to today at the Classy Lanes Stables Training Centre in Puslinch, Ontario, bringing down the barn's roof and walls on the horses inside.
Some 50 firefighters were dispatched to the scene, but intense cold froze water hoses, hampering their efforts, Puslinch fire chief Steve Goode told the CBC television network.
The cause of the fire was not immediately known.
The stable's owners were on vacation in Florida at the time of the blaze.