Emergency services were called to a fire in Furnace Green, Crawley, after an arson attack on a storage unit containing tools.
Sussex Police and fire crews from Crawley and Horsham attended the fire at a Barratts house building site in Furnace Drive at 4.42am today (Tuesday February 25).
The fire damaged three temporary offices, including the site office which had been broken into.
Firefighters were in attendance for around three hours.
A spokesman for Sussex Police said: “Enquiries are being made to establish what has been stolen and into the fire, which is being treated as deliberate.”