Babine Forest Products in Burns Lake, B.C., alleges that Toshiba manufactured and supplied the motor that sparked the fire leading to the explosion in January 2012.
In a B.C. Supreme Court statement of claim, Babine Forest Products alleges electrical arcing in a conveyor motor ignited combustible material, causing the blast.
The explosion killed workers Carl Charlie and Robert Luggi, and injured 20 others.
None of the allegations contained in the statement have been tested in court.
The lawsuit claims Toshiba, as well as two companies listed as ABC Company No. 1 and ABC Company No. 2, were negligent because they failed to manufacture the motor to a reasonable standard.
"The defendants, and each of them, breached the condition in that the motor was not reasonably fit for the purpose but contained faults and defects rendering it unfit," the court document said.
The lawsuit alleges the piece of equipment had faulty wiring, and other components of the motor made it susceptible to premature failure and/or ignition of nearby combustible material.
The statement of claim also alleges Toshiba, ABC Company No. 1 and ABC Company No. 2 did not inspect or test the motor, warn users of the risk of arcing, or control the quality of suppliers and sub-contractors that provided the parts.
Last week, WorkSafeBC released a nearly 90-page report that suggested the initial spark that led to the fatal sawmill fire likely occurred in the mill's basement, an area that was "known to be very dusty."
The motor believed to be at the centre of the lawsuit and a gear reducer that were enclosed by a guard sat in the basement area.
The safety agency's theory is that friction caused accumulated sawdust in the guard to smoulder. The report said the guard was oddly constructed, as the clearance space between it and the gear reducer was tighter than usual.
The smouldering then turned into an open flame, said the report.
"At a certain point, the dust in the air was ignited by the flame within the guard of the motor-reducer assembly, deflagration of the dust took place, and a catastrophic explosion occurred," the report said.
The WorkSafe report said the motor had been installed by a contractor, while the wiring for the machine was completed by mill electricians.
The Crown said two weeks ago that an outside expert who also conducted an investigation did not definitively determine an ignition source, saying the combustible sawdust could have been ignited by a number of things, including an open flame, metal-halide lights or electric arcs.
Both investigations agreed, though, that once the airborne dust caught fire, it burned quite violently and the explosion blew a large fireball through the roof.
The WorkSafeBC report said the explosion could have been prevented had Babine taken action to control wood dust. The report noted the company knew it had an inadequate dust collection system, even after a similar explosion and fire occurred almost a year earlier.
The Crown said no charges would be laid in connection to the blast, partly due to a questionable investigation by WorkSafeBC. Investigators failed to obtain search warrants and inform people of their rights, the prosecutors office said.
BC Coroners Service announced on Tuesday that it will hold a public inquest into the deaths of Charlie and Luggi.
A news release said chief coroner Lisa LaPointe believes examining the circumstances surrounding the explosion may help prevent future deaths in similar situations.
A presiding coroner and a jury are expected to hear evidence from subpoenaed witnesses. While the jury can't make findings of fault or legal responsibility, it can make recommendations.
The Babine Forest Products mill has been rebuilt and is expected to return to full production soon.
Neither Hampton Affiliates, the Oregon-based owner of the mill, nor Toshiba were available for comment.
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