Police were called to Sullivans Scrap Yard in Hunston by West Sussex Fire and Rescue Service after reports of an arson attack.
Firefighters put out the fire which caused no damage apart from two scorch marks on the ground.
The incident happened in the evening of Monday, August 13.
A spokesperson for Sussex Police, said: “Bottles were found near the marks which are believed to have been thrown in to start the fire so it is believed to have been started deliberately.”
Sergeant Alan Ward said: “We are treating this as arson and are investigating what happened around 11pm on Monday. Anyone who saw anything suspicious in the area or has any information is asked to contact police on 101 quoting serial 1837 of 12/8. Alternatively contact the independent charity Crimestoppers anonymously on 0800 555 111.”