Investigators are treating a massive field fire in Northampton on Tuesday evening as arson.
Emergency crews were called out at around 4pm to the blaze in a field in Kingsthorpe.
A spokesperson for Northamptonshire Fire and Rescue Service said: "Crews were called to reports of a large bonfire out of control on fields behind Teviot Close in Kingsthorpe earlier this afternoon at 3.56pm. Shortly after arrival a gas cylinder exploded, causing the fire to spread further across the field.
"Six appliances from The Mounts, Mereway, Moulton, Brixworth, Wellingborough and Rushden all attended the scene to help extinguish the flames.
"Crews used two ultra-high pressure lances, four hose reel jets and one main jet to help douse the flames and bring the scene under control.
"Between 25,000 and 30,000 square metres of standing crop were destroyed by the fire. The initial cause of the blaze is believed at this stage to have been a deliberate ignition," the spokesperson added.
Anyone with any information about the cause of the fire is urged to call police on 101.