Fire crews have been tackling a fire at the former Fleetwood Health Centre
The alarm was raised at the disused building on London Street at around 7pm.
Crews had to dismantle boarding around the roof of the building so they could get in to tackle the flames.
Station Manager Lister Howarth told Radio Wave, they expected to be at the scene damping down into the evening with a full investigation into the cause now underway.
Detectives are helping fire officers find out how the fire started.