A child and 14 adults are being taken to hospital after being found in the back of a freezer lorry at a service station on the M25.
Officers were called to Clacket Lane services, between junctions 5 and 6 of the motorway, at 10.15am on Friday after reports "of concern for safety" over a group of suspected illegal immigrants who were discovered in a vehicle, a Surrey Police spokesman said.
The driver of the white HGV, who was travelling northbound, stopped at the service station after reporting that he had heard loud banging coming from inside.
Fifteen people were discovered in the rear of the lorry and are being taken to hospital for medical checks.
Surrey Police officers closed the main slip road into the petrol station while the people were detained on suspicion of illegal entry.
The lorry driver is assisting police with enquiries and the investigation will be passed on to UK Visas and Immigration, the spokesman added.