New photos and fire inspection reports released by Prince George Fire and Rescue show the levels of dust in the Lakeland mill raised concerns prior to an explosion that killed two men and injured 24 others.

The cause of the April explosion and fire at the central B.C. sawmill has not been released by investigators, but dust levels have been raised as a possible cause and remain part of the investigation.

The inspection reports were obtained by the Vancouver Sun newspaper though a Freedom of Information Act request and posted online.

The inspection reports dating back to 2008 flagged dust levels at the mill as an ongoing concern, but also say inspectors were partially satisfied with efforts to clean up the dust just a month before the fatal explosion.

"There are certain parts of the mill that have excessive amounts of accumulated fine wood dust," said the November 2011 report by fire prevention officer Steve Feeney, who is with the Prince George Fire Service.

"I am requesting a policy be developed and adopted that describes the procedure, frequency, and documentation for the cleanup and removal of this combustible hazard."

A followup inspection dated March 19, 2012, indicated Feeney was partially satisfied by the mill's cleanup, but still had concerns about the lack of a long-term plan.

"Your efforts to reduce the amount of accumulated fine wood dust on the building and machinery surfaces did not go unnoticed. The unacceptable amount of dust that was present during the fire inspection on November 29, 2011, has been significantly reduced," he wrote.

But the fire inspector noted he still had not received a copy of the dust cleanup policy he requested the mill operators develop. He also raised concerns about the placement of fire extinguishers at the mill.

Fire inspection reports flag dust accumulation at the mill as a concern as early as September 2008 and again in September 2010.

"Continue with a scheduled maintenance of programs for all high hazard areas and areas that are affected by fine wood dust," said the September 2008 inspection report.

Cause still undetermined

The cause of the Lakeland mill explosion has not been determined, but some outside experts have pointed to high dust levels from milling dry pine beetle wood as a possible cause.

The Lakeland sawmill in Prince George, B.C., was destroyed by an explosion and fire in April (Submitted by Todd Wikjord)

Safety inspection reports by WorkSafeBC released in May also showed inspectors found piles of wood dust throughout the mill as recently as February, although they appear to be mainly concerned about the possible health effects.

The records note the mill operator was told by WorkSafeBC to prevent the accumulation of "hazardous amounts of wood dust."

High dust levels have also been suggested as the cause of a similar explosion at a sawmill in Burns Lake in January that killed two workers. The cause of the Burns Lake explosion has also yet to be determined.

Most of the logs being processed at both mills were dry wood that had been killed by beetle infestation long before they were harvested.

After the second explosion at the Lakeland mill, the provincial government ordered all B.C. sawmills to remove accumulated sawdust.