A police officer was injured after being called to an illegal rave in a field involving 4,000 people, police said today.
Wiltshire police were called last night to farmland near Warminster, in Wiltshire, where ravers had set up sound stages.
Officers have been deployed throughout the night to clear the site of up to 4,000 ravers in what is thought to be the biggest rave the force has had to deal with.
A 46-year-old male officer was hit by a car at the site, off the B390 between Knook and Chitterne, and suffered a suspected fractured ankle.
He was taken to Salisbury District Hospital where he will undergo surgery later today.
Police have warned members of the public to avoid the area as hundreds of cars have been left by the side of the road causing congestion.
Spokesman for the force, Steve Coxhead, said raves normally attract several hundred people rather than thousands.
"Such events take no account of the safety of those who attend or the inconvenience caused to local communities or the travelling public on which they can have a substantial impact especially over a bank holiday weekend," he said.
"Many of those attending the rave have simply abandoned their vehicles on the side of the road which has caused local traffic disruption with traffic diversions being put in place at Heytesbury, Codford, Chitterne, Tilshead and Shrewton.
"The public are asked to stay away from the area and regrettably the disruption is expected to continue for some hours to come."