The fire started around 8pm yesterday evening near Houghton Bridge, onlookers said.
Nearby residents reported hearing a ‘small, muffled explosion’ during the blaze, which fire crews reportedly attended around 8.20pm.
“We had been looking out of the window at the last of the sunset,” said Alex and Gregory Halls, who lived nearby. “We saw the smoke behind the station and ran to see where it came from. When we arrived the caravan was fully ablaze.”
The fire service said crews from Arundel and Littlehampton attended a mobile holiday home at Houghton Bridge, Amberley.
One hose-reel, one jet, two thermal-imaging cameras and two sets of breathing apparatus were used to fight the blaze.
They were called shortly before 8pm and left around 9.20pm. There were no reported injuries.