Dayton fire officials said the fire appeared to involve foam roofing materials on the top of the six-story building, called CareSource Center City, located at East First and North St. Clair streets.
RELATED: Dayton Fire: CareSource fire involves roofing materials
The building will be first newly constructed office tower in downtown Dayton in about a decade.
According to Dayton fire officials, everyone was able to get out of the building safely, and the only people believed to have been inside at the time the fire started were construction workers.
The heavy black smoke rising over downtown may have looked dramatic, but the fire was not particularly large or hazardous, said Dayton fire Chief Jeffrey Payne.
“This wasn’t a dangerous fire because it was outside and well ventilated,” he said.
The fire started shortly after noon on Thursday and was basically extinguished within 90 minutes, officials said. The fire would have been knocked out much sooner if it had not been six stories up.
PHOTOS: CareSource construction site on fire in downtown Dayton
Foam insulation stacked on top of the building apparently caught fire when work being done underneath it heated and ignited the materials, said Payne.
The biggest danger was that the burning foam would melt or warp the metal decking and overheat the supports, potentially leading to a collapse, he said.
But though some of the metal decking did warp, no parts of the structure collapsed, Payne said.
Crews put out the fire using the 137-foot aerial ladder truck. Firefighters also cooled the decking and hit hot spots with hoses.
Troy Erbes, vice president of the company constructing the new building, said all employees and construction workers are accounted for and there were no injuries.
“We had an incident on the roof of the building,” said Erbes, VP of Danis. “Some roof insulation caught on fire.”
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A time-lapse of the fire in downtown Dayton
Erbes said they are working to determine what ignited the fire. Danis and fire staff plan to sit down to discuss best construction practices and go over how to avoid future issues, fire officials said.
CareSource’s operations were not affected by the fire, and the organization does not believe the fire will delay the construction or opening of the new building, said spokeswoman Fran Robinson.
CareSource said in a statement it still planned to open its new downtown Dayton campus in the spring of 2019.
Construction started last year on the building, which is expected to house more than 600 employees.
“Family and friends of those who work in our four CareSource buildings in downtown Dayton should know that the fire did not approach any of our other buildings,” Robinson said.
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The new tower is being built at the site of the former Patterson Co-op High School on the 100 block of East First Street.
CareSoure has become a major employer in Dayton, anchoring downtown with its employment base of nearly 2,000 workers.
Along with its 230 N. Main St. headquarters, CareSource bought a building it had been leasing called Ballpark Village, across from Fifth Third Field.