Firefighters from Bedford and Kempston were called to a blaze at the European Oat Millers on Mile Road, Bedford on Tuesday evening.
A fire had broken out in the kiln on the third floor of the processing plant which spread through ducting and ventilation systems to the sixth floor.
The fire was contained there and did not spread to the structure of the building.
The crews dismantled the ducting system and used breathing apparatus and jets to extinguish the fire.
Thermal Imaging Cameras were also used and the aerial platform was in attendance.
Station Commander Derek Hobbs was at the incident and said: “This was a very tricky fire to deal with but the crews worked with the building staff to quickly identify the areas affected and bring the fire under control.
“The Fire Service will be re-inspecting the building later today.”