Firefighters say they are surprised the nine-story shell of the Butternut factory building had not collapsed during the overnight fire in the historic Old Market area in downtown Omaha.

The old structure was gutter by the four-alarm blaze reported about 11:30 p.m. Wednesday night. The fire also spread to at least two adjacent buildings by Thursday morning.

Fire officials say there were not believed to have been any occupants in any of the three buildings.

The fire spread quickly throughout the building, which was being converted into an upscale condominium complex. Those units were expected to be available beginning this spring.

Firefighters expected the building to smolder for several days.

There are no reports of injury.