Police believe a caravan at Lakeside Holiday Park was deliberately set alight in the early hours of Saturday.
Updating a previous report, a Sussex Police spokesman said they believe the fire was started deliberately.
The fire service attended the 3.27am incident and is investigating, along with police.
A Lakeside resident, who wished to remain anonymous, said: “It looks like it might have done quite a lot of damage. It’s very worrying.”
The fire service said: “The investigation is still ongoing.”
A police spokesman said: “It is believed the fire may have been started deliberately.”
The caravan was 20 per cent damaged by fire and 50 per cent by heat and smoke.
A spokesman for the park owner said the caravan was unoccupied and used for demonstration purposes.
They added: “We would like to express our thanks to the local fire services who quickly and efficiently extinguished the blaze.
“There were no injuries, and we will assist any enquiries being made as to the likely cause.”