Twenty-one people, including children as young as 12, have been found inside a refrigerated lorry entering the UK.
The group, thought to be from Vietnam, was concealed among a load of sparkling water at the port of Newhaven in Sussex on Thursday.
Details of the Border Force operation have only just emerged, but a criminal investigation is under way.
A Romanian man, believed to be the driver, has been charged with assisting unlawful entry into the UK.
It had earlier been reported 15 children had been found in the lorry, but the figure was later revised by the Home Office.
A spokesman said the group included 17 people claiming to be aged between 12 and 17 who "presented themselves as Vietnamese".
"A total of 11 were later confirmed to be minors. They were passed into the care of social services," he said.
A spokesman for East Sussex County Council added: "Age assessments were carried out... and concluded that five were in fact adults aged over 18."
He said the children were placed with foster carers or in supported housing.
One of the children had since absconded from council care, he said.
The lorry was stopped on its arrival from Dieppe in France.
The children did not require medical treatment.
The adults - five women and five men - were interviewed by immigration officials, the Home Office said.
An 18-year-old man and a woman aged 27 have been removed from the UK.
The eight other adults, aged between 21 and 28, have been told they must report regularly to the Home Office while their cases are assessed.
Andrut Duma, 29, appeared before magistrates on Saturday accused of immigration offences and has been remanded in custody until a hearing at Lewes Crown Court on 26 November.