Motorists are facing up to six miles of queues on the M20 after police discovered a body on the road.
Police were called at 6.05pm on Tuesday evening to the London-bound carriageway between junctions 10 and nine near Ashford.
Highways England has confirmed that the road remains closed will remain closed for ongoing investigations.
At present, the road closure is affecting travel to the Eurotunnel and access to the Port of Dover.
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Passengers are being allowed a two-hour window to board after their allotted departure time, Eurotunnel has said.
P&O Ferries, meanwhile, has urged passengers to use alternative routes.
A large green screen has since been put up where the body was found.
A line of police officers wearing white protective covers on their feet could be seen slowly walking the stretch of the carriageway towards the screen and looking at the ground.
On the opposite side of the carriageway, nearer to junction 10, one lane of traffic has reopened after a crash involving five cars and a lorry.
Witnesses at the scene said they had been at a standstill for about two-and-a-half-hours.
The driver of the lorry, a 42-year-old man, has been arrested on suspicion of dangerous driving and remains in police custody.
A woman was also airlifted to a London hospital with injuries and a man was taken to a local hospital following the crash.
Firefighters were called to free two people from their cars, Kent Fire and Rescue Service said.
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.
Detective Chief Inspector Richard Vickery said: ‘I would like to hear from motorists who have dashcam footage taken between 5.30pm and 6.30pm on Tuesday February 20 of the M20 London-bound carriageway between junctions 10 and nine.
‘I would also ask motorists who used the M20 after 6pm on Tuesday to contact us if they believe they experienced anything unusual whilst driving and check their cars for signs of a collision.
‘We do not underestimate the impact that closing this stretch of the motorway has on people and I thank them for their patience. It is crucial that we ensure that all evidence is collected. As soon as the motorway is reopened the opportunity to collate potentially crucial information is lost.
‘We are working tirelessly at the scene and I am hopeful a lane of the M20 will be re-opened later today.’