A disused building in Woodlands Close, Five Oaks, near Billingshurst, was deliberately set alight at around 5.10 this morning (Friday 12 August).
West Sussex Fire and Rescue rushed to the blaze to find a 15 by 15 metre derelict house destroyed by fire.
Emergency vehicles from Billingshurst, Horsham, Cranleigh and Haywards Heath were drafted in to douse the blaze.
Teams left the scene around 9am and building is to be demolished.
A fire investigator confirmed it was started deliberately.
PC Andrew Li said: “Arson is incredibly dangerous and can easily have tragic consequences.
“Whilst this building was disused, trees and bushes surrounding the property could easily have caught alight and spread the fire. Neighbours were fearful that their own property would catch fire and of the falling debris.
“It is believed someone gained access to the building over the past few weeks and stole a boiler, possibly for scrap metal, which may be linked to the arson.
“Anyone who may have seen any suspicious behaviour over the past few weeks is asked to contact police immediately.”
Police are conducting house-to-house inquires as part of the ongoing investigation.
Anyone with information is asked to contact Sussex Police on 0845 60 70 999 quoting serial 201 of 12/8 or anonymously to the independent charity Crimestoppers on 0800 555 111.