Motorists on a major link to the Channel tunnel and the port of Dover experienced miles of tailbacks after a body was found on the road and a separate collision forced police to close the M20 motorway in both directions.
Officers were called to the London-bound carriageway between junctions 10 and nine, near Ashford, Kent, at 6.05pm on Tuesday after a body was found. The person was pronounced dead at the scene.
Then at 8am on Wednesday four cars and a lorry were involved in a collision on the coast-bound carriageway, forcing it to be closed to all traffic. One lane has since been reopened.
A woman was airlifted to a London hospital with injuries and a man was taken to a local hospital after the crash.
A 42-year-old man who was driving the lorry has been arrested on suspicion of dangerous driving and remains in police custody.
Witnesses at the scene said they had been at a standstill for about two and a half hours.
By 10.30am on Wednesday drivers were experiencing six miles of queues back to junction 11 on the London-bound carriageway and the road closure was affecting travel to the Eurotunnel terminal and the port of Dover.
The London-bound carriageway of the M20 between junctions 10 and nine has since reopened, according to Kent police.
The Kent and Essex serious crime directorate, which investigates incidents including murder and organised crime, is working with road collision investigators to determine the cause of death in the first incident, which is being treated as unexplained.
DCI Richard Vickery said: “I would like to hear from motorists who have dashcam footage taken between 5.30pm and 6.30pm on Tuesday 20 February of the M20 London-bound carriageway between junctions 10 and nine.
Kent police want to trace a silver Nissan Qashqai that was on the motorway between 5.30pm and 6.30pm on Tuesday.
A large green screen had been put up where the body was found and a line of police officers wearing white protective covers on their feet were seen slowly walking the stretch of the carriageway while examining the surface.