A lorry driver is being questioned after 27 suspected migrants were found in the back of his vehicle on the M6.
Some of the group fled from the vehicle but were detained by officers before being given a medical assessment and transferred to immigration officials for interview.
The 42-year-old driver was arrested on suspicion of facilitating the illegal entry of persons unknown to the UK, Staffordshire Police said.
The incident caused traffic chaos as the motorway was closed in both directions, between junctions 15 and 16 for Stoke-on-Trent, and between junctions 16 and 14 for Stafford on the southbound carriageway.
The M6 has since reopened.
Burton Albion fans travelling to their Carabao Cup semi-final against Manchester City were among those stuck in the traffic.
Hundreds travelling to the Etihad missed the game which kicked off at 7.45pm.
In a statement Staffordshire Police said "An investigation is continuing tonight after 27 people were detained following a vehicle stop on the M6 earlier this evening resulting in total closure of the motorway.
"Officers from Staffordshire Police stopped a lorry on the M6 northbound carriageway between Junctions 15 and 16 at around 5.45pm following concerns for people travelling in the back of a vehicle.
"During the incident, a number of people fled from the lorry but all were detained.
"Thankfully, there were no serious injuries reported.
"The driver of the vehicle, a 42-year-old man was arrested on suspicion of facilitating the illegal entry of persons unknown to the UK."
Danny Ellis, who was a few hundred yards from the incident, said he saw 30 to 40 police cars pass him on the northbound side of the motorway and said three or four lorries were stopped and searched.
"We could only see the lorries being chased down and stopped but we couldn't see people running away," he said.
"We were told for safety to get back in our cars and lock them.
"We were told a lot of people escaped and ran from the back of these lorries."
The 30-year-old, who works in the telecoms industry, said he could see men being treated by ambulance medics on the floor.