UK police said six people had been taken to hospital, and two men arrested, after "several people" were found Friday in a lorry aboard a ferry in southern England.
The incident at Newhaven, in East Sussex, sparked a major response from emergency services, with Border Force, police and several ambulances all attending.
Police have not yet confirmed precisely how many people were discovered in the truck, or commented on their condition.
"We are supporting Border Force after several people were found in a lorry on a boat in Newhaven Port," the force said on X, formerly Twitter.
"Six people have been taken to hospital for treatment."
It added one of the two men had been arrested on suspicion of facilitating illegal entry to the UK, and the other for illegally entering the country.
Migrants have stowed away in lorries to reach Britain going back decades, but public attention in recent years has shifted to the emergence of arrivals across the English Channel on small boats.
Both routes are considered extremely dangerous and have proved deadly on multiple occasions.
The perilous nature of people-smuggling in lorries was underlined by the death of 39 Vietnamese migrants found in the back of a truck in southeast England in 2019.
The victims -- the youngest of whom were two 15-year-old boys -- suffocated in the truck's container as they were being transported to what they had hoped would be new lives in Britain.