Neighbours told CBC News that they heard an explosion around 8 a.m. on Sunday.
Volunteer firefighters, they said, could only watch as the station burned.
Fire crews from other stations in East Gwillimbury were called in to extinguish the blaze.
At noon, the station was still smouldering.
A nearby legion is being used to provide drinks and snack for crews from other stations who are working to put out the fire.