Avon and Somerset Police say they have stopped a lorry containing 20 people suffering from possible dehydration.
The vehicle was stopped at a service station off the A303 at Southfields roundabout near Ilminster, Somerset at about 1pm.
"Their health and welfare is paramount as we try to piece together with the immigration authorities exactly what has happened," a police statement said.
More top news
Parliamentary inquiry finds thousands of children could fall prey to sexual exploitation and gangs because of flawed warning systems.
David Cameron said the June 23 referendum is the most important vote young people will place in their lifetimes.
Plan would leave steelworkers worse off in retirement - but not as worse off as those in other pension schemes.