The blaze battered the 40 x 20 metre barn on Bukehorn Road, Thorney in the early hours of Sunday morning (March 26) after a deliberate start to the fire.
The barn contained farm machinery and around 300 tonnes of potatoes.
A Cambridgeshire Fire and Rescue Service spokesman said: “Four crews from Thorney, Standground, March and one from Crowland in Lincolnshire, together with a water carrier from Ramsey, was called to a barn fire in Bukehorn Road.
“Firefighters use a Multistar appliance to access the roof in order to cut away roof panels to gain access and provide ventilation after the fire spread to 500 pallets inside the building.”
Fire crews were at the scene throughout the night to monitor the building but the fire continued to burn for more than 24 hours.
It came only two days after fire services were called to tackle two bales on fire at the same location.
Anyone with information of either incident is urged to contact police on 101 or call Crimestoppers anonymously on 0800 555 111.