Court documents show Sunrise Propane and its directors, Shay Ben-Moshe and Valery Belshov, have been found guilty of nine provincial-offences charges in relation to the explosion.
The court ruled Sunrise failed to provide safety training and a safe working environment, discharged a contaminant and contravened a number of provincial orders related to the cleanup after the August 10 blast.
Story continues below slideshow
The court also found Ben-Moshe and Belahov failed to take all reasonable care to prevent the company from flouting those orders.
Ontario government lawyers argued training negligence in a fireball that killed employee Parminder Saini, 25, and rained debris on the surrounding area. A responding firefighter died of a heart attack.
The explosion displaced some 12,500 residents 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.