Seven hundred people attended an illegal rave in Bedfordshire overnight.
It took place in a barn off Stondon Road in Meppershall.
Police prevented one van with a generator and music equipment from reaching the site - but another got through.
The police helicopter was deployed but so far there have been no arrests. 150 people are still at the site.
Illegal ravers who occupied an empty factory building in Cambridgeshire are thought to have caused up to fifty thousand pounds of damage.
The New Year's Eve rave at the warehouse in March was attended by around five hundred people.
Watch Stuart Leithes' report
Police in Norfolk and Suffolk are cracking down on illegal raves, asking people to report any suspicious behaviour in the run up to the bank holiday weekend.
Those planning an illegal event are being warned that their sound equipment will be seized, and they will be prosecuted.
The police say information from the public is invaluable.
Police in Bedfordshire closed down an illegal rave at a farm barn in Dunton during the early hours of Sunday morning.
Around 300 people are thought to have attended the rave, which began at around 12.30am.
Local residents alerted police to the disturbance and officers moved in to set up road blocks around the area.
As the main ravers began to clear the scene they were arrested for causing a public nuisance and their equipment and vehicles were seized.
Police officers worked through the night to negotiate an early and safe end to an illegal rave in a field off White Horse Lane, in Trowse. 150 people attended the event.
Numerous complaints were received by local residents around midnight.
The music was switched off at approximately 9.15am on Sunday 18th March. One arrest has been made for the possession of drugs.