The fire was reported shortly before 2:30 p.m. Wednesday at the state capitol building at 411 Legislative Ave.
Police said the exhaust pipe, located in the attic, caused nearby combustibles to ignite during a full-load test of the building's backup generator, located in the basement.
[Ads /]
The fire extended from the basement to the attic and roof line, but the backup generator was not damaged, police said.
The fire was placed under control around 3:40 p.m.
A police officer was rushed to Kent General Hospital where he was treated and released. A firefighter was treated at the scene.
The General Assembly in on break until January so there was a limited number of staff in the building.
The building was scheduled for reopen Thursday.
Police are investigating.