Police are working to disperse an illegal rave at Twyford Woods in Lincolnshire, where some 500 revellers are still at the party.
More than 1,000 people were at the illegal rave overnight on Saturday, May 23, just off the A1 near Bourne in south Lincolnshire.
When Lincolnshire Police arrived at the site last night at 11pm, they found a large illegal rave setting up.
As previously reported, when officers tried to intervene, they came under attack from a crowd of around 200 people, who threw bottles and other objects at them.
Two police officers and a police dog were hit by the missiles from the crowd and suffered minor injuries.
Another police officer was struck by a car he was trying to prevent from entering the grounds of the illegal rave.
He suffered serious injuries, but they are not life threatening.
Overnight, police confiscated a sound system from the rave and also arrested a man and three young women (aged 18, 20 and 21) from Norfolk.
A continued police presence is at the site as Lincolnshire Police work with neighbouring forces to disperse the illegal rave.
Chief Superintendent Stuart Morrison said: “Because of events we policed elsewhere, we had a larger number of officers on duty than we normally would have. We took a decision to try to close the event because it is illegal and it’s not safe.
“What we are trying to do now is to dissuade or prevent other people from joining it. We don’t want it to get bigger. We want to close it down, and then investigate the criminal conduct that is taking place here.
“We do not want the public to be further inconvenienced by this carrying out longer than it has to, so our plan is to close it down as soon a possible.
“Anyone thinking of attending this illegal rave shouldn’t. This is not legal and we are looking to close it. Generally, people would be better to avoid the area until you return things to normal.”