A HOAX bomb led to the closure of the M25 Dartford Crossing between Kent and Essex for more than seven hours, police have said.
The cylindrical device, with wires, was found on a Dover-bound coach after a man got off just after it had gone through the toll booths on Friday.
The 27-year-old foreign national raised suspicions after he ran from the scene to a rough area nearby.
He was detained by security personnel at a nearby distribution depot.
The suspect was arrested at 16:15 BST on suspicion of making a bomb hoax.
Kent Police said the man made threats about a device on the coach.
The male, from the Bournemouth area, continued to be questioned in custody.
He was detained under the Mental Health Act.