BURNS LAKE, B.C. -- Three mill workers were injured Thursday in a fire and explosion at a northern British Columbia wood pellet plant, which was the site of a less serious explosion two years ago and was recently fined for "repeated" safety violations.

Leroy Reitsma, the president of Pinnacle Renewable Energy Inc., said the incident happened at about 8 a.m. at a facility operated by the company near Burns Lake.

One worker suffered serious injuries and two workers received minor injuries, said Reitsma, though he declined to offer more details about their injuries. The RCMP described all three workers' injuries as serious but not life threatening.

Reitsma said Thursday's fire and explosion originated inside a drying machine during a maintenance shutdown, though he said it was far too early to speculate about the cause. The company is investigating and WorkSafe BC had dispatched prevention officers to the scene.

The wood mill industry has been under increased scrutiny since two fatal explosions in 2012 at facilities in Burns Lake and Prince George. Both explosions were linked to the presence of combustible wood dust.

Reitsma said the company still did not know what caused Thursday's fire and explosion, but he said the fact that it occurred inside a piece of equipment appeared to set it apart from issues related to controlling the buildup of wood dust.

"I'm not ruling anything out at this point, but as the event occurred inside of equipment, there is some differentiation from the issue that's been focused on in terms of housekeeping," he said.

The plant was the site of another explosion in 2012, Reitsma said. No one was injured in that incident, which occurred in a different area of the plant, he said.

The company has been cited several times in the past year for dust buildup at several facilities, including the Burns Lake plant.

The WorkSafe BC website indicates two fines were handed out to the company in May of this year, both for about $49,000.

The fines each related to potentially explosive dust.

"The firm's failure to control and remove hazardous accumulations of combustible dust that could cause a fire or explosion was a repeated and high-risk violation," said a summary of one of the fines.

The company also received fines for dust levels at facilities in Quesnel and Strathnaver, both south of Prince George.

Reitsma declined to comment about the fines. He said the Burns Lake plant is currently in compliance with provincial regulations.

WorkSafe BC was unable to provide any more details about the facility's inspection history.

A cloud has been hanging over the province's mill industry the 2012 explosions in Burns Lake and Prince George, which were just months apart and each killed two workers.

Subsequent investigations determined the explosions were fuelled by dust from dry, pine beetle-infested wood.

The explosions led to tougher regulations designed to keep dust under control, as well as increased inspections at wood mills.

The companies that owned the mills were both fined, but Crown prosecutors declined to approve charges, in part due to problems with how WorkSafe BC conducted its investigations and collected evidence.

A government report released in July made a series of recommendations to overhaul such investigations to ensure evidence would stand up in court.

WorkSafe BC spokesman Scott McCloy said the agency has yet to launch a full investigation into Thursday's fire and explosion at the Pinnacle plant, so he couldn't say whether the earlier recommendations would affect how the case is handled.

McCloy said the agency plans to release a report detailing its progress on those recommendations soon.