RUMFORD – A fire destroyed a maintenance building at the MeadWestvaco paper mill Tuesday, shutting down paper machines and forcing workers out of part of the mill.

The fire was reported shortly after 4:30 a.m. in a wooden building that housed maintenance offices, storage areas and an air-conditioning repair shop.

Fire Chief John Woulfe said investigators determined that the building collapsed and somehow ignited a fire. The fire in turn is believed to have caused acetylene and oxygen tanks inside the building to explode, he said.

At one point, flames shot up three stories high, said Gary Hemingway, president of Local 900 of the Paper Allied Industrial Chemical Energy Workers International Union. Smoke billowed above the mill and into other buildings.

The building that burned was attached to the old part of the mill, but the fire was contained before it could spread.

Emergency and town officials said the fire was contained by 8:30 a.m. Two employees were taken to Rumford Memorial Hospital to be treated for smoke inhalation.

The mill’s three operating paper machines, as well as a pulp dryer and finishing machines, were shut down and part of the mill evacuated, said Steven Hudson, the mill’s director for manufacturing services.

One of the machines was back up and running in the early afternoon, and the others were expected to be operating in the evening, Hudson said. He didn’t expect the fire to have any further impact on operations. Still, the fire set off concerns throughout the mill.

“Any time there’s a fire at a paper mill, we take it very seriously,” Hudson said. “Between the product we’re making and storing and our raw material, there’s a lot of combustible material.”

Woulfe said investigators think the building, which was among the older structures in the mill complex, may have collapsed because of weight from ice on the roof.

He said company officials were assessing the damage to put an estimate on the loss.