Ottawa fire crews are investigating the cause of a fire at 9 Leeming Drive, in the city's west end.
Fire crews were called to the address, which happens to be St. Thomas Catholic School, before 9:00 p.m. Monday.
Fire fighters located what they thought was the main body of the fire and put it out, but crews inside the school were reporting heavy smoke, and so a third alarm had to be called.
Crews confirmed the fire was contained to the floor of the gymnasium and had the fire under control by 9:50 p.m.
The cause has yet to be determined. No one has been reported hurt.