Multiple fire crews responded to a fire in Walton Street in Aylesbury.
Seven appliances and crews attended (three from Aylesbury, one from High Wycombe, Leighton Buzzard, Hemel Hempstead and Berkhamstead), along with three officers.
Firefighters were called to the smell of smoke in a 12-storey non-domestic building. Firefighters searched the premises and located a fan heater fire within a ground floor cupboard. The fan heater was isolated.
Firefighters used small tools and thermal imaging cameras.