BUCKSPORT – A fast-moving fire in two coal silos Monday morning caused an estimated $150,000 in damage to a portion of the International Paper Co. mill.

The silos have no crews working in them and no one was injured in the blaze. The fire did not interrupt production at the mill.

The fire was reported in the silos about 7:50 a.m., according to Capt. Mike Denning of the Bucksport Fire Department.

Denning said firefighters could see smoke from the fire as they left the fire station.

“We looked out over the houses and we could see the black smoke, so we knew we had a working fire,” Denning said.

There was a lot of fire inside the silos when firefighters arrived, Denning said. The towers stand 120 to 150 feet, well beyond the reach of the Fire Department’s ladder truck. Firefighters were forced to mount an interior attack on the flames.

Denning said they had to climb the catwalk that runs next to the enclosed conveyor belt up to the top of a tower. The power was out, so the use of handheld lights was necessary.

“It’s a long walk up there,” he said. “It’s dark. You could see the glow at the end of the tunnel and you just kept walking toward it.”

Firefighters carried hoses with them up the 35-degree incline, and waited to use their air packs until they got near the top in order to conserve air, Denning said.

It was a complicated fire to fight, he said.

Although the mill has not burned coal since it began operating a natural-gas-fired turbine last year, residual coal dust remains inside the silos. In addition, oil lines that ran through the tower burst, adding more fuel to the fire. The conveyor belts, used to move coal to and from the towers, also caught fire. According to Denning, that was one of the big dangers of this fire.

The conveyor runs from the coal silos to a fuel-mixing tower. Other conveyors carrying other types of solid fuel, including bark and wood waste, also run through that tower, where another conveyor carries them into the main section of the mill.

“The towers are located in a fuel-handling area,” said IP spokesman Keith Cunningham. “We needed to make sure that the fire didn’t spread along one of those other conveyors to the main part of the mill, or back to the different fuel storage areas.”

There were some spot fires along the conveyor between the coal silos and the fuel-mixing tower, Denning said, but crews from the mill’s fire brigade worked their way back along the conveyor to ensure that they did not go beyond.

“If it had gotten to the main mill, we would have had a big problem,” Denning said.

It took about an hour to bring the fire under control, Denning said, and crews remained on the scene to watch for flare-ups.

The cause of the fire was still under investigation later Monday, although investigators for the mill and the Fire Department were looking at a bearing housing located at the top of the coal tower. Denning said the bearing may have overheated and sparked the fire.

Investigators also will try to determine why the fire did not activate one of the sprinkler systems inside the tower. The sprinkler at the bottom of the tower worked, he said, but the system at the top of the tower did not.

Most of the damage was limited to the coal silos and the small mechanical building atop the tower. Denning estimated the damage at $150,000, although Cunningham said mill officials were still assessing the damage.

Cunningham said the mill needs to ensure that it can use coal for fuel in case there is a problem with the mill’s natural gas supply, but said mill officials had not yet determined what to do about the damaged silos.

Crews from Orland and Orrington provided assistance to the Bucksport firefighters.