Part of the M20 will be closed until at least midday on Wednesday after police found a body on the road.
Officers were called at 6.05pm on Tuesday to the London-bound carriageway between junctions 10 and nine near Ashford.
A body was found on the road and the person was pronounced dead at the scene, Kent Police said on Tuesday night.
The death is being treated as unexplained and the force is appealing for anyone who saw a pedestrian in the area to come forward.
Highways England tweeted that the road will likely remain closed for ongoing investigations following "a very serious incident".
#M20 closure J9-J10 UPDATE. If you're within closure please remain with yr vehicle. Our officers and colleagues from @kentpoliceroads will be u-turning traffic from back of the queue to head back to J10 but please be patient, it'll take some time to get everyone out of closure.
— Highways England (@HighwaysSEAST) February 20, 2018
Pictures circulated online showed long queues of traffic at a standstill and Highways England told people to remain in their vehicles until police officers directed them to turn around.
Some took to Twitter to vent their anger after claiming drivers were parking in the hard shoulder and blocking emergency services from getting past.
M20: ‘Serious’ incident M20 Londbound J10 to J9. Traffic stopped. pic.twitter.com/I770q1wAyn
— Kent 999s (@Kent_999s) February 20, 2018
The motorway provides a link to the Channel Tunnel and ports of Dover.
P&O Ferries tweeted to warn drivers to use an alternative route.
Anyone with information should call the Kent Police serious collision investigation unit on 01622 798538 quoting 20-0913.