A fire that destroyed a portable classroom at a Scarborough high school early Monday was an accident, according to the school's principal.

An investigation by the fire marshal determined that the fire at R.H. King Academy was an electrical fire and not arson, R.H. King Academy principal Tommy Jutcovich told CP24.com Monday afternoon.

Firefighters were called to the school at 3800 St. Clair Ave. E., near Kingston Road, at about 3 a.m. when people who live in the area noticed the flames.

Fire crews encountered massive flames in a portable room behind the school, Toronto police said.

Firefighters were able to save five other portable classrooms. Those portables will not be used for some time because they are without electricity. The fire damaged hydro wires that feed the portables.

Classes that would have been held in the portables will now be held in the main school building, Jutcovich said.

A damage estimate hasn't been calculated.

Anyone with information about the fire is asked to call 43 Division or Crime Stoppers.

With a report from CP24's Cam Woolley