Arsonists torched two vehicles in Godmanchester on Monday.
Firefighters from Huntingdon were called to reports of a blaze in Gumcester Wat at about 6pm.
A spokesman for Cambridgeshire Fire and Rescue Service said: "The crew arrived to find one car and one van on fire. Wearing breathing apparatus, firefighters used two hose reels to extinguish the fires before returning to their station by 7.10pm."
An investigation revealed the cause of the fire to be deliberate.
Anyone with information should contact police by visiting www.cambs.police.uk to submit an online report or call Crimestoppers, anonymously, on 0800 555111.