A fire that destroyed a Catholic school's trades training centre has been blamed on an "overheating engine compartment".
The blaze at Guilford Young College, which took hold on Monday afternoon in the northern Hobart suburb of Glenorchy, sent a plume of black smoke into the air and sparked an alert from Tasmania Fire Service (TFS) for nearby residents.
CCTV from the workshop, released on Tuesday, shows smoke emanating from a car in the workshop. Less than 10 minutes later, fire can be seen under the vehicle.
In a statement on Tuesday, TFS said it had determined the fire "started from an overheating engine compartment in a car that was being stored in the building".
"The engine compartment of a car caught fire a short time after it was driven into the workshop, and the fire quickly spread to the rest of the building, fuelled by gas cylinders, cars, and workshop and building materials," said Regional Fire Investigator, Station Officer Adam Doran.
"Fire crews contained the fire to the school's trade training centre building and were successful in stopping it from spreading to other parts of the school, with the added support of Hobart Fire Brigade's new aerial firefighting platform."
Witnesses reported hearing explosions during the emergency.
Station Officer Doran said the fire — estimated to have caused damage in the value of "multi-millions" — was particularly difficult to control due to the high fuel load in the building.
"At the peak of the fire, five fire crews were in attendance with career crews supported by volunteer crews from the greater Hobart area," he said.
"A firefighter who was treated at the scene for heat exhaustion did not require further medical treatment."