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.
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Thames Valley Police named the victims as Savaan Mundae, Jaspal Bahra, Thanh Nguyen and Captain Michael Green.
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