Bucksport firefighters spent about 2.5 hours fighting a fire at the former Verso Paper mill on River Street on Thursday. Credit: Nick Sambides Jr.

BUCKSPORT, Maine — A fire damaged part of a building being demolished at the former Verso Paper mill site on Thursday. No one was injured.

Smoldering debris ignited in a 10-by-20-foot dust collection silo at a building identified by Bucksport firefighters only as Tower III. A passerby on Route 15 saw black smoke coming from the area, which is near the site’s north gate, and drove a half-mile to the fire station to report it at about noon, fire Capt. Pam Payson said.

Payson said she didn’t know why demolition workers taking down parts of buildings at the River Road site off Route 15, which is known locally as Main Street, failed to report the fire.

Site owner American Iron and Metal, a scrap metal recycler, is razing buildings on the 250-acre property to make way for a proposed $250 million indoor salmon farm and a continuing education annex proposed by Maine Maritime Academy. Both deals are pending, Town Manager Susan Lessard said.

Once firefighters arrived, the workers were helpful, Payson said. They took apart portions of the dust collection silo so firefighters could get at the flames, Payson said.

The fire heavily damaged the silo and extended into a lower-level garage area before firefighters doused it, Payson said.

Four or five demolition workers assisted firefighters, she said.

The fire likely started amid debris in the silo. Workers on Tuesday were doing “hot work” — cutting away portions of the building — which likely created sparks that smoldered, Payson said.

Firefighters spent about 2½ hours on the site, Payson said.

The demolition work continues. Jeff McGlin, a vice president at AIM Development USA, estimated in December that the work was about 70 percent complete.

“All of the former pulp and paper mill assets [that] were in the scope of demolition [have been] completed,” he said in an email in December. “The last phase of demolition is the former steam plant.”