A "large quantity of fuel" has caught fire during a barn blaze that has been declared a major incident.
Six fire crews are tackling the blaze at Rame Head near Torpoint in south east Cornwall.
Firefighters said gas cylinders were exploding as they tried to stop flames reaching a fertiliser store nearby.
No casualties have been reported, and roads in the area have been closed as the public are asked to "stay clear".
Cornwall Fire and Rescue Service said in a statement: "The barn measures 40m by 30m and is well alight, including a quantity of fuel and gas cylinders, some of which have exploded.
"Due to the rural nature of the area, roads have been closed to allow access for emergency vehicles and members of the public are asked to stay clear."
The first emergency calls were received at about 13:40 GMT on Wednesday, with firefighters from Torpoint, Saltash, Looe, Liskeard, Launceston and Plympton in attendance.