The M25 was shut in both directions tonight as officers dealt with a man in the carriageway near the Clacket Lane services.
Surrey Police also reported that an ambulance worker was assaulted in the same incident, although it is unclear what caused the disturbance.
The closure is near Caterham and Sevenoaks, south of London. Police have advised commuters to "approach the services with care."
Despite the police warnings, the closure has brought chaos for rush-hour commuters on the London orbital route, and it is unclear when the motorway will reopen.
Several commuters have vented their frustration on Twitter, posting pictures of the huge queues they were facing.