Two people were taken to hospital after 18 stowaways were found in the back of a lorry on the hottest day of the year so far.
The stowaways waved to alert passing motorists who flagged down the HGV driver to stop on the A22 in East Grinstead, West Sussex, at around 9.20am on Saturday.
Immigration enforcement officers found 18 people who said they came from Iraq, Syria and Iran. A male and a female were taken to hospital with dehydration, but were later discharged.
Six people claiming to be children were passed to social services to have their age assessed. A Home Office spokesman said: "All will be processed in line with immigration rules."
Sussex Police said those who did not need hospital treatment were given water and medical aid. The nearby Trinity Methodist Church was used as a refuge centre as immigration officers arrived.
The lorry driver, a 63-year-old man of no fixed address, was arrested on suspicion of facilitating illegal immigration. He was in police custody.
With temperatures in East Grinstead hitting 25C on Saturday, police said it was vital that they reacted quickly to free the stowaways from the lorry.
Sergeant William Keating-Jones, of Sussex Police, said: "Our priority was for the welfare of the occupants who were in the back of the lorry. The vehicle was exceptionally hot and it was important we reacted quickly.
"This was a great multi-agency response to a potentially life-threatening situation, with emergency services, immigration officials, volunteers and even local residents all pulling together.
"We were also mindful of causing minimal disruption to motorists, and the road was closed for about 20 minutes while we were at the scene."