The call came in at about 11:45 p.m., when an employee at the building at 814 Northern Lights reported heavy smoke inside, firefighters said.
Thirteen units ultimately responded to the two-story building and began battling the blaze in the roof of the structure and wrestled it under control just before 1 a.m., the department said. It was fully out at 1:17 a.m.
An investigation revealed the fire had begun smoldering earlier in the day, when a crew was working on the roof, said Jen Collins, fire department spokeswoman.
The crew apparently used a torch to install a heat seal and inadvertently ignited some plywood, which began smoldering until the fire fully erupted late Thursday, she said.
Damage was estimated at about $10,000.
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