Sixteen people have been arrested after police received reports of migrants in the back of a lorry on the M1.
Hertfordshire Police were called at 2.55pm as the vehicle headed north towards Bedfordshire. The lorry was stopped just past junction 11.
Police said none of those arrested are thought to be seriously unwell.
The case will now be handed to the UK Border Agency.
Sky Correspondent David Bowden said it was not yet clear how the presence of the migrants in the lorry became known.
He added: “If they are refugees then what tends to happen is as soon as they get onto UK soil, they jump out of whatever vehicle they’re in, give themselves up and claim asylum.
“If they don’t do that, if they’re economic migrants, they try to get to wherever it is they think they want to go and then disappear into the community.”
No details about the migrants’ ages or nationalities have been released.