A lorry from Turkey was stopped near a busy roundabout and searched by officers from the National Crime Agency.
The top cops are believed to have removed at least two men from the back of the lorry, but it is not yet known whether they are suspected illegal immigrants.
Several uniformed police officers also attended the incident, which took place around 11.40am this morning on the Newport Road, off Kingston roundabout.
Traffic came to a halt as an unmarked police car parked in the middle of the road to block the lorry’s path.
“It seemed an awful lot of police for a case of suspected illegal immigrants. And it also seems strange that the National Crime Agency would be involved,” said one eyewitness.
Witnesses saw a man believed to be the driver of the lorry led off by police. Two more men sat on the grass verge and were later taken away in a police vehicle.
The lorry, marked Fullsped international Transport, contained clothing hanging on racks in the back.