Police say they were attacked as they tried to break up an illegal rave at a warehouse near Bristol, as BBC reports.
Officers who were called to Yate at around 22:30 GMT on Saturday said up to 700 people were there.
Some of the crowd began acting violently towards officers and threw objects when they were told to leave, Avon and Somerset Police said.
The site was cleared by Sunday afternoon after eight people had been arrested and music equipment seized.
A force spokesman said when officers arrived they “found a number of vehicles and several hundred people” at the site.
“Roads approaching the area were closed to prevent more people reaching the site by car, but large numbers of people continued to arrive on foot from several different directions,” he said.
The spokesman said some people became hostile towards the police.
“Items, including lit spray cans and bottles, were thrown at police, some of whom were injured but remained on duty,” he said.
Mains power was cut to the building, but an alternative source was being used the spokesman said.
The eight people arrested include a man in his 30s who was held on suspicion of being involved in organising the event.