Arsonists set fire to a large quantity of timber at the Huntingdon branch of B&Q on Thursday night.
Firefighters were called shortly before 10.30pm to the St Peter’s Road retail park after reports of a blaze at the rear of the DIY store.
A spokesman for Cambridgeshire Fire and Rescue Service said: “A quantity of timber was well alight to the rear of B&Q and firefighters used a hose reel to extinguish it.”
An investigation revealed that the cause of the fire was deliberate. Anyone with information should contact the police on 101 or the independent charity Crimestoppers anonymously on 0800 555111.