About 15 explosions were heard in the next hour, with blasting fuel barrels - many 50-gallon drums filled with bulk oil - flying about 50 feet into the air, he said. One burning barrel landed on and ignited an adjacent building.
"We backed off, for the firemen's safety," Paulson said. "There's a lot of explosions going on."
Two firefighters suffered minor injuries at the scene, and one was transported to an area hospital, Paulson said.
Paulson said the fire was "not at all" contained around 8:30 p.m. and crews expected to be on site through the night. The fire was reported about 3:30 p.m.
Crews were worried about two 6,000-gallon fuel tanks, one filled with diesel fuel and one with gasoline, that were on site, Paulson said.