A spokesman for Norfolk Fire and Rescue Service told FoodManufacture.co.uk that the fire was “substantial.”
Richard Herrell, group manager from Norfolk Fire and Rescue Service (NFRS), added that it was a "very challenging fire".
Fire crews reached the factory soon after the blaze started at 1.30pm on Tuesday November 8.
No one was injured in the blaze which was finally extinguished in the early hours of Wednesday November 9.
Staff were evacuated from the factory and nearby buildings at Burnet Road, Sweetbriar Industrial Estate. The intensity of the fire also required the closure of nearby roads.
NFRS confirmed that it had concluded its investigation of the cause of the fire but could not release details.
Meanwhile, BBC News Norfolk reported that the fire was started by a ham smoker.