Five people arrested over an illegal rave over the weekend have been released while inquiries continue.
Officers alerted by advertisements on social media on Saturday evening later found about 600 people, at the event on Massingham Heath, Grimston, Norfolk.
They monitored it through the night and disrupted it at about 15:45 on Sunday.
Three men, aged 25, 28 and 31, were arrested in connection with organising the event.
Police then received further calls from residents complaining about noise and the event was discovered.
About 150 vehicles were on site throughout the night and specially trained officers went in to disrupt the event and seize sound equipment.
Two other men, aged 20 and 33, arrested at the scene on suspicion of drug driving have also been released under investigation.
Temporary Assistant Chief Constable Nick Davison described the operation as "significant" and said the event was closed down safely.
He said officers had been working closely with landowners and would continue to do so.
"Raves, not uncommon at this time of year, can be very disruptive for local residents and landowners while the presence of hundreds of people and vehicles can also have a detrimental impact on the environment," he said.