Plum Creek Timber Co. officials say a bearing failure led to the explosions and fire at the company's fiberboard plant in Columbia Falls.
Plum Creek spokeswoman Kate Tate said Friday that a catastrophic failure of a bearing on a raw material feed line ignited both wood fiber and the belt last Tuesday.
Tate tells the Daily Inter Lake (http://bit.ly/SJ5gbg ) that heat from the fire ignited the insulation on a duct pipe carrying wood fiber, which then caused the fiber on the inside to catch fire.
The burning wood fiber then caused a series of explosions in the ductwork at the sprawling seven-acre plant.
No damage estimates have been completed, but Tate said equipment damage was minimal.