A lorry driver is being questioned after 27 suspected migrants were found in the back of his vehicle on the M6.
A part of the motorway was closed in both directions after police stopped and searched the lorry at around 5.45pm on Wednesday.
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, who was arrested at the scene, was arrested on suspicion of facilitating the illegal entry of persons unknown to the UK, Staffordshire Police said.
Burton fans travelling to their Carabao Cup semi-final against Manchester City were among those stuck for hours in the traffic.
Hundreds were yet to arrive at the Etihad as the game kicked off as planned at 7.45pm.
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 told the Press Association.
“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.
He was driving to the football with a friend when both carriageways of the motorway were closed between junctions 15 and 16, near Stoke-on-Trent on Wednesday afternoon.
“We’ve been stuck here still for three hours and we’ve been told 10pm,” he said at around 8pm.
The northbound carriageway reopened shortly before 10pm, according to Highways England.
Staffordshire Police said: “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.”