Firefighters were called to an arson attack at the former RAF Upwood site last night (Wednesday).
Crews from Huntingdon and Chatteris attended the base shortly after 9.30pm following reports that a bonfire had been started within one of the derelict buildings at the site.
It is the latest in a long-running series of similar arson attacks at the base in recent years.
A spokesman for Cambridgeshire Fire and Rescue Service said: "Firefighters arrived to find an unattended bonfire in a derelict outbuilding and extinguished it using a hose reel. They returned to their station by 10.55pm."
An investigation determined that 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.