A portion of a building under construction collapsed in a Richmond, Va., suburb Wednesday, and at least 12 workers were feared pinned under the rubble.

Despite reports by construction supervisors at the site that all 12 were accounted for because they were eating lunch, Chesterfield County Fire Lt. Matt Coffin told reporters that the dozen or so missing actually hadn't been located yet.

Rescue crews were stabilizing the structure and preparing to gingerly enter the crumbled condominium to listen for anyone who might be trapped or buried, according to Coffin.

"We expect to be here for many, many hours," he said at a Wednesday afternoon news briefing. "This whole structure behind me is considered unstable."

His account contradicted that of the operations manager of a drywall company working on the condominium.

Dennis Harden of A. Pertozzi Inc. told local media that the 12 workers thought to be inside the building were on a lunch break and all had been accounted for.

Harden said one worker was taken to the hospital with a leg injury, but it isn't life-threatening. He said he had spoken to the crew supervisors overseeing the building's heating, air-conditioning and electrical systems and they had told him they'd tracked everyone down.

The condominium building in Chester, Va., was next to the town's library. Everyone in the library has been accounted for, according to local TV reports.

Coffin said 911 dispatchers were told that a dozen workers were inside when a 60-foot-section came crashing down Wednesday.

The two-story wood structure is part of Chester Village Green, a mixed used development. The community is about 15 miles south of Richmond.

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FOX News' Catherine Donaldson-Evans and The Associated Press contributed to this report.