WHITE CITY — A fire atop a 130-foot pile of sawdust near the Biomass One facility sent a thick column of smoke high above White City on Saturday.

The day's 100-degree temperatures and a late afternoon breeze helped push the fire across the sawdust mound, Jackson County Fire District No. 3 Deputy Fire Marshal Don Hickman said.

District 3 officials believe the fire sparked on the pile's north side and sent embers swirling to a field west of Biomass One.

"We had spot fires up to 1,000 feet away that turned into small grass fires," Hickman said.

District 3 and Medford Fire Department crews attacked the fire with ladder trucks, which hosed down the sides of the pile from high in the air.

"The goal was to use the wind to push the water, making a kind of rain storm," Hickman said.

Firefighters worked the blaze for close to two hours. At one point, a large swath of the mound's north face glowed with swirling columns of flame.

From the highway, the mound resembled a small volcano with a thick tendril of smoke rising high above the surface.

The burning sawdust produced a dense smoke that crept across Highway 62, at times reducing visibility on the busy highway.

Biomass One workers used bulldozers atop the mound to bury the flames in fresh sawdust.

Hickman expected the workers would spend the night monitoring the fire for flare-ups.

The cause was not known, Hickman said.

"These large piles have fires burning inside them at all times because of heat, compression and air," Hickman said. "The fires usually stay below the surface, but at times will break out and this is what will happen."

Jackson County sheriff's deputies blocked off Avenue G while crews worked the blaze.

District 3 and Medford fire were assisted by the Oregon Department of Forestry and the U.S. Forest Service.

Reach reporter Chris Conrad at 776-4471; or e-mail cconrad@mailtribune.com.