Toronto Fire Services has determined that a stovetop burner left in the "on" position is the cause of the fire at 650 Parliament Street Wednesday morning.

That morning, a third party was testing the electrical system in the building. When the electricity of the unit was turned on, the material left on the stovetop caught fire, Toronto Fire Services said Friday in a news release.

Toronto Fire Services and the Electrical Safety Authority (ESA) conducted an investigation that determined the ignition of a stovetop burner must have been left on after the building was evacuated last year.

In August 2018, an electrical fire that caused structural damage and ruined the electrical system forced more than 1,500 tenants to vacate the apartment building.

"The tenants are still unable to return to their homes while the building's electrical system is being upgraded," according to the news release.

Tenants who have questions regarding when they will be able to return to their homes are asked to refer to the building's landlord.