Four engines were sent to reports of a fire at a vacant single storey commercial building in Dominion Way, Worthing, at 5.10pm today.
A command support team from Bognor also attended the scene.
The building, which measured 15m by 15m, has been 75 per cent destroyed by the fire, according to the spokesman.
Firefighters have now left the scene, the spokesman said.
SEE MORE: Four crews tackle fire in Worthing