Police have begun lifting road closures after an illegal Boxing Day rave was cleared on Friday.
Revellers flocked to Candover Bridge in Dartmoor’s National Park on Thursday evening and set up a makeshift stage and sound system.
But their cars caused chaos in the area, blocking off roads and limiting access.
Chief Supt Matt Longman said paramedics had been blocked from attending an incident because of the gridlock.
He added: ‘There was at least one medical incident that we could not get an ambulance to, this person was eventually taken to hospital. This highlights the importance of maintaining public safety.
‘We have now re-opened roads as members of the public leave the location and the area is cleared.’
Police said they had arrested two people.
A 27-year-old man from Kingskwerwell, South Devon, was held on suspicion of driving under the influence while an 18-year-old man from Winterslow, in Wiltshire, was arrested on suspicion of possessing Class A and C drugs.
One reveller said the party was inspired by Brexit while another insisted all mess would be cleared up.
The man, who wanted to be known as Ross, said: ‘Everyone that you see here will be extremely incorporated with the Extinction Rebellion protesters and do not want to see anything wrong happening with Mother Earth.
‘It’s just us coming on public land, having a party, cleaning up, leaving, nothing is left.’
Police were reportedly administering breathalyser tests on a number of attendees as they left the area.