A fire involving flammable butane gas at Crockway, Maiden Newton, is suspected to have been an arson attack.
Police and fire officers believe the cause to be "suspicious".
Firefighters from Dorset & Wiltshire Fire and Rescue Service were called at around 4.33pm to the blaze yesterday afternoon, in an outbuilding containing butane cylinders.
In a post shared on Facebook, a spokesman for the fire service said: "Upon arrival we found a caravan well alight involving two seven kilo butane cylinders with a further cylinder nearby."
Crews worked at a safe distance to keep the cylinders cool using a ground monitor - a type of large hose.
Two fire engines from Dorchester and one from Weymouth attended the scene.
The spokesman aded: "Once the fire was out and we’d established that the cylinders were cool enough to be safe, we made the general area safe to hand back to the landowner."
One fire crew remained at the scene while they awaited the arrival of Dorchester Police and Southern Electric.
"The incident was handed over to Dorset Police as we believed ignition to be suspicious", the spokesman said.
Dorset Police said officers attended the scene after being contacted by the fire service at around 6pm.
"The fire was reported to have been started suspiciously", a police spokesman said. "We made enquiries but no arrests have been made at this stage."
Anyone with information is asked to contact police on 101 quoting information number 11:395
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