A blaze which needed 20 firefighters to tackle 10 tonnes of flaming hay has sparked an arson investigation.
The fire took hold on Saturday night at the Lower Farm barn in Swingate Lane in Berkhamsted.
Fire crews from Hemel Hempstead, Berkhamsted and Kings Langley were quickly on the scene and battled to bring it under control.
It is believed the bale blaze, which is still smouldering, started between 3pm and 4pm, with police treating it as arson. No one suffered injuries.
Investigating officer, DS Paul Perkins, said: “I am appealing to anyone who was in the area around the times the fire is thought to have started and saw anything suspicious please get in touch.
“Any information, no matter how seemly insignificant, could help us with our enquiries”.
Call 101 with information. Alternatively contact Crimestoppers anonymously on 0800 555 111.