A lawyer representing thousands of Torontonians affected by a deadly 2008 propane explosion says a report by the Ontario Fire Marshal's office confirms allegations made in a multi-million dollar class-action suit that he hopes the court will certify this fall.

Harvin Pitch, a lawyer from Stevensons LLP who is representing about 10,000 residents whose homes were damaged following a massive explosion at Sunrise Propane on Aug. 10, said the report has found the blast was accidental and resulted from a prohibited truck-to-truck transfer and gas leak.

"The fire marshal concluded our theory of the case. Basically, the explosion happened because of a truck-to-truck transfer which was prohibited by the regulator," Pitch said in an interview with ctvtoronto.ca.

"That cause is what we say happened. We say the people are liable because a dangerous activity was taking place and an accident resulted. In law, that's sufficient."

Two people were killed after a mushroom cloud erupted over the Murray Road facility, near Keele Street and Wilson Avenue. Toronto fire chief Bob Leek died at the site and the body of part-time Sunrise employee Parminder Singh Saini, 25, was pulled from the wreckage.

An investigation by the Technical Standards and Safety Authority (TSSA), which carries out inspections on behalf of governments, found that an employee was engaging in banned truck-to-truck propane transfers prior to the explosion.

The practice of transferring propane directly from one tanker truck to another is prohibited in Ontario because it is believed to increase the risk of a gas leak or fire.

The investigation further found that the truck-to-truck practice was a "frequent and routine" operating practice at the facility, according to the TSSA.

Pitch believes the TSSA must be held accountable for not enforcing an order prohibiting truck-to-truck transfers.

"It was contrary to their code and they had ordered it stopped, but it continued," Pitch said.

"If a regulator is authorized to enforce its order and doesn't, it is negligent in law."

Officials conducted a province-wide audit of propane facilities following the explosion.

If the class-action suit, estimated to cover up to $300-million in damages, is certified by the court at the end of November, residents whose homes were damaged as well as those who suffered injury may be eligible to make a claim, Pitch said.