Crews from across the region are currently responding to reports of a fire at Dithmarschen Way just off Penwinnick Road, St Austell.
Fire and rescue crews from St Austell, Lostwithiel, Truro, Bodmin, Launceston and Falmouth are in attendance at the building fire.
A Cornwall Fire and Rescue Service spokesperson said: "A fire has been located on the first floor of a two storey derelict building. Firefighters in breathing apparatus are using main jets to extinguish the fire."