Arsonists set fire to 100 tonnes of straw in a field in Eye.
Fire crews were called to the blaze in a field next to the A16 in Whitepost Road at 1.40pm.
Firefighters used a ground monitor to dampen surrounding hedgerows to protect the area and returned to their station by 3:55pm.
Crew Commander Quinton Roach said: “The smoke wasn’t affecting the A16 so we let the fire burn out and will be inspecting the site throughout the night.”
The cause of the fire was deliberate.
Anyone with information should contact the police on 101 or Crimestoppers anonymously on 0800 555111.