West Sussex Fire said firefighters were sent to Chilgrove Road shortly after 9pm.
A spokesperson for West Sussex Fire and Rescue Service said: “We were called to reports of a fire involving a commercial building off Chilgrove Road in West Dean at 9.12pm last night (22 April).
“Our crews from Bognor Regis, Chichester, East Wittering and Midhurst were mobilised to the scene along with Hampshire Fire & Rescue Service crews from Bordon and Emsworth and the Aerial Ladder Platform from Southsea.
“Firefighters wearing breathing apparatus brought the fire under control using five jets, compressed air foam and a hydrant.
“We had a crew on scene throughout the night keeping a watching brief, with relief pumps brought in at 4.45am this morning. We remain in attendance at the scene at this time.”