Witnesses described a "ball of flame" high above the sky visible for kilometres following the explosion in April, 2012 that killed two people and injured 24 others.
The company that owned the mill was fined $724,000 by WorkSafeBC last July, but appealed the decision.
No criminal charges were ever laid in the deaths of Alan Little, 43, and Glenn Roche, 46, because of concerns over the admissibility of WorkSafeBC evidence.
Crown counsel said WorkSafeBC's investigation did not properly gather evidence to determine to what extent management was aware of the risk of an explosion from sawdust accumulations at the mill and what action was taken to mitigate that risk.
Today's inquest is a formal court proceeding, with a five-person jury. It's meant to publicly review the circumstances of the deaths. However its main goal is to determine facts, not fault.
"It does let the community know exactly what happened," said Barb McClintock, with the BC Coroners Service.
"[It] reassures them that deaths of any members of their community are going to be taken seriously and aren't going to be covered up."
Ronda Roche, who lost her husband in the explosion, is expected to testify.
"We know a lot of facts, but we realize there's a lot we don't know. Hearing them in such a public forum is going to be very difficult for us," she said.
In December the mill re-opened after being entirely re-built.
Another inquest into two more deaths at a mill explosion in Burns Lake — also in 2012 — starts in July.