Cambridgeshire Fire and Rescue Service have confirmed that a large fire on an industrial estate in St Neots was started deliberately.
A police investigation has been launched after 20 firefighters from around St Neots, Gamlingay, Kimbolton and Sandy in Bedfordshire, attended the incident in Forge Close at around 2:40am on New Year's Day.
Cambridgeshire police are now appealing for information following the incident.
The fire is believed to have started at just after 12.20am, with an estimated £40,000 worth of damage caused after pallets of plastic pellets were set alight, with the flames also damaging vehicles parked at neighbouring sites.
A spokesman for the fire service said: "One motorhome, two vans and eight cars were involved in the fire and there was heat damage to adjacent buildings. Crews were at the scene until 5.40am."
The investigation has concluded the fire was started deliberately. Anyone with information should contact police by visiting www.cambs.police.uk to submit an online report or call Crimestoppers on 0800 555111, quoting reference 35/124/20.