Fire ripped through Bolsover District Council's old offices last night.
Emergency services were called to the Sherwood Lodge site on Oxcroft Lane, Bolsover.
A Derbyshire fire service spokesman said: "Firefighters from Bolsover, Staveley and Chesterfield attended the incident.
"They gained access to the derelict building using cutting tools and a ladder.
"Once inside, they extinguished the fire, which was in the first floor of the building.
"Crews had left the scene by 11pm."
The fire service requested police attendance, the spokesman added.
However, a Derbyshire police spokesman could not find details of the incident when asked this morning.
The district council moved to High Street in Clowne in 2013 in a bid to cut costs.