A report by a provincial investigator has determined that a fire at a St. James Town highrise that forced hundreds of people from their homes last year was caused by an electrical failure that led to an explosion.

The report by Ontario's Office of the Fire Marshal and Emergency Management was released to Toronto Fire Services on Monday.

"The OFMEM determined that a catastrophic failure of the electrical system in the building caused an explosion in the electrical room, and smaller explosions and fires throughout the building," Toronto Fire said in a statement.  

The August 21, 2018 fire triggered a six-alarm response by the fire department and resulted in the evacuation of around 1,500 residents, many of whom are still waiting to return to their units.

The fire caused extensive damage and necessitated complex repairs estimated at around $50-60 million.

After multiple postponements, it is expected that residents may be able to return to their units in November, more than a year after they were forced to evacuate.

Toronto Fire said that they will be reviewing the full report, as well as fire engineering reports in order to fully understand their conclusions.