On Monday (16) at 1.37am, two crews from St Neots were called to a car fire on Bishops Way, Great Paxton.
The crews arrived to find two cars well alight, which was spreading to a house. Wearing breathing apparatus, firefighters used two hose reels to extinguish the fire.
All persons were accounted for.
The crews returned to their station by 3.45am.
The cause of the fire was deliberate. Anyone with information should contact police by visiting www.cambs.police.uk to submit an online report or call Crimestoppers on 0800 555111.