A driver has been arrested after 13 men and boys, including a 15-year-old, were discovered in the back of a lorry.
Three of those found in the insulated lorry were taken to hospital suffering from heat exhaustion, West Midlands Ambulance Service said.
Paramedics, an air ambulance and police officers were called after 2pm on Thursday to Mangrove Service Station, on the A45 London Road, in Rugby, Warwickshire, and discovered the men inside the lorry, which is from Romania.
The 26-year-old driver has been arrested on suspicion of people trafficking, Warwickshire Police said.
The Border Agency has been informed and the remaining people, eight of whom were aged between 15 and 39, were taken into custody.
A West Midlands Ambulance Service spokesman said: "Crews arrived to discover 13 patients who had been travelling on the back of a lorry.
"All of the patients were male, with three of them receiving treatment at the scene for signs of heat exhaustion before they were transferred to University Hospital Coventry and Warwickshire on land ambulances.
"None of the injuries are thought to be serious."