A sniffer dog uncovered 11 suspected Iraqi illegal immigrants attempting to enter the UK on a lorry bound for Basildon in Essex.
The Romanian-registered vehicle was stopped at Calais on 7 June.
UK Border Agency officers found the cord that secured the trailer doors had been tampered with and a sniffer dog detected a scent.
Officers searched the vehicle and found the men who were refused entry to the UK and handed to French authorities.
The driver of the vehicle and the company could now face a fine of up to £2,000 for every stowaway if they are found not to have taken adequate steps to secure the load, the UK Border Agency said.