One crew from Chatteris was called to a well-developed fire at Longwood Hill Drove, Chatteris involving 400 tonnes of bailed straw and a car.
The crew assessed the situation and made a decision to allow the fire to safely burn out. They returned to their station by 6.50pm.
The cause of the fire was deliberate. Anyone with information should contact police on 101 or Crimestoppers on 0800 555111.