The motorway closure follows a police chase just after 11.25am. Bomb disposal experts are attending as a “precautionary measure” due to “concerns about the security” of the vehicle.
Police said officers attempted to stop the vehicle on the M20 “coastbound” near Junction 12.
Police said the vehicle was “travelling at excess speed”.
The vehicle left the motorway before returning to the London-bound carriageway.
It was stopped at Junction 9 when a police car made “tactical contact” to end the pursuit.
“It was pursued to Junction 9 where a police car made tactical contact with the vehicle, bringing it to a stop with no injuries reported.
“A 27-year-old man from Wales was arrested on suspicion of dangerous driving and failing to stop for police.
“The motorway has been closed to allow for the carriageway to be made safe for road users, who are advised to find alternative routes if possible.
“The British Army’s Explosive Ordnance Disposal team is also currently at the scene as a precautionary measure following concerns about the security of the subject vehicle.”
Highways England said motorists stuck in queues are being turned around.
Diversions are in place around the closed sections of the motorway.