Dramatic pictures show hundreds of tyres going up in flames - with plumes of thick black smoke which could be seen for miles.
Fifty 999 calls were made to the fire service about a blaze involving 200 tonnes of agricultural tyres in north Dorset.
Police said today 'extensive damage' was also caused to a barn and forklift unit.
Officers arrested a 15-year-old boy on suspicion of arson in connection with the incident.
He was later released from the investigation without charge.
Picture: Shaftesbury Fire Station
Dorset & Wiltshire Fire and Rescue Service were called to Rifles Lane in Shaftesbury at 7.10pm on Thursday.
Local residents were advised to keep their windows closed.
Two crews from Shaftesbury attended along with firefighters from Gillingham, Tisbury and Poole, supported by water carriers from Yeovil and Poole.
Five main jets, one hose reel jet and two foam jets were used to extinguish the blaze.
The fire affected an area of around 40m x 20m.
It was under control with no more resources needed by 9.45pm but a crew from Sturminster Newton remained on the scene through the night.
A firefighting crew is on site today.
While the cause of the fire is still to be confirmed, police are treating the incident as suspicious.
A 15-year-old boy has been arrested on suspicion of arson and is assisting officers with their enquiries.
Detective Constable George Graham, of Weymouth CID, said: “We are making enquiries into this incident and I am appealing for any witnesses to come forward.
“I would like to hear from anyone who was in the area at the time and witnessed any suspicious activity.”
Police later said the teenage boy arrested had been released from the investigation without charge.
Contact Dorset Police on 101 quoting occurrence number 55180109957.
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