Major crime investigation as body found on Kent M20
The London-bound M20 has been closed since the body was found near Ashford, Kent, just after 18:00 GMT on Tuesday.
Officers from the Kent and Essex Serious Crime Directorate are investigating the death, which is being treated as unexplained.
Long traffic queues have built up in the area. The M20 serves the Channel Tunnel and the Dover ports.
Ferry company P&O has urged passengers to use alternative routes and Eurotunnel is giving people a two-hour window to board after their allotted departure time.
A large green screen has been put up where the body was found, and forensics officers have been examining the road surface.
Earlier, the coast-bound carriageway was also closed after a crash involving five cars and a lorry in which two people were injured. One lane has since reopened.
Witnesses have said they have been at a standstill for two-and-a-half hours.
The London-bound carriageway remains closed between junctions nine and 10, with diversions in place.
Travel reports said police had to wait for daylight to carry out their investigations.
Det Ch Insp Richard Vickery has appealed to motorists to check dashcam footage from Tuesday evening, and to report anything unusual or any signs of a collision on their cars.