Twelve people have been found in the back of a lorry on the M25 after police were alerted by concerned members of the public.
Emergency services were called to the motorway near Chertsey, Surrey, in southern England, after receiving reports at about 11am on Thursday that people were on board and struggling to breathe.
Surrey Police officers stopped lorries to find the correct one. Eleven men and a woman, believed to be migrants from Ethiopia, were found inside a vehicle.
Traffic was "backed up for miles" as a result of the incident, a witness said.
Motorist Melissa Bell was travelling eastbound on the M25 to Leatherhead when traffic ground to a halt.
"There was a lorry which had been stopped by multiple police cars and there were ambulances there, too," Ms Bell said.
"There were numerous East African-looking men. Some were lying face-down on the hard shoulder and some sat up with masks on.
"I just couldn't understand it. I've never seen anything like it."
Surrey Police said the lorry was stopped between junctions 10 and 11 on the anti-clockwise carriageway about 11.30am. Two lanes of the motorway were closed while officers dealt with the incident.
The roads policing unit confirmed both junctions reopened about 1.45pm.
"Officers were given a very limited description of a lorry and were told that people on board were struggling to breathe," a force representative said.
"This resulted in police needing to stop a number of lorries quickly to try to identify the one involved."
The suspected migrants were checked by paramedics at the roadside before being taken into police custody.
The matter will now be dealt with by immigration enforcement.
"The government is tackling illegal immigration and the harm it causes, often to the most vulnerable people, by removing those with no right to be in the UK," Immigration Minister Chris Philp told Sky News.
"We continue to work with law enforcement agencies and tackle illegal migration in all its forms.
"Our New Plan for Immigration will speed up the removal of those who have entered the UK illegally."