Sunrise Propane has been convicted of violating environmental regulations in connection with a 2008 blast in north Toronto that killed a man and forced thousands from their homes.
Courts documents show the company and its directors, Shay Ben-Moshe and Valery Belshov, have been found guilty of numerous provincial-offences charges in relation to the explosion.
Ontario government lawyers argued training negligence in a fireball that killed employee Parminder Saini, 25, and rained debris on the surrounding area.
The August explosion displaced some 12,500 and caused millions in property damage.
Court has heard Saini was "incinerated" during a risky truck-to-truck propane transfer, while fellow employee Felipe De Leon escaped from the blast.
A defence lawyer argued that Saini and De Leon had received training and were responsible for the explosion.
The class-action trial against Sunrise, Ben-Moshe and Belahov, started in February 2012. Both directors and the company could face millions of dollars in fines at sentencing.