Police investigating an illegal rave on farmland in Essex have bailed 34 people who were arrested on suspicion of conspiring to cause a public nuisance.
Police clearing the site on Sunday morning
Violence broke out at the event on Saturday, involving up to 600 people.
Essex Police said an officer suffered a severed fingertip, a patrol car was burnt out and missiles were thrown during clashes at Great Chesterford.
A police spokeswoman said six people arrested had been released without charge and 34 others bailed.
Nine officers were hurt during the operation, with injuries including head and leg wounds, and two revellers suffered head injuries, police said.
At one point, 40 people attempted to cross the nearby M11 motorway on foot.
Emergency roadblocks were erected and the motorway speed limit reduced to 40mph.
Forces from Essex, Suffolk, Cambridgeshire, Norfolk and Hertfordshire were involved in the operation.
The landowner had not given permission for the party and it had no entertainment licence.