Six men who tried to enter Britain illegally hidden in a lorry packed with crisps were discovered before the vehicle left France, the UK Border Agency said.
Specially trained detection dog Sam alerted officers working in Dunkirk that people were hiding in the Polish registered vehicle which was driven by a Pole and was heading for Bradford.
Three Iranian men, two Vietnamese men and one Iraqi man were found hiding in the trailer which was packed with food, including large bags of crisps.
The men were removed from the vehicle before it entered the UK and were handed to the French authorities.
The vehicle was then allowed to continue its journey.
Brodie Clark, head of the UK Border Force, said: "The UK Border Agency has officers working 24 hours a day in Calais using specially trained dogs as well as the latest technology to identify and prevent illegal immigrants from reaching the UK.
"This is another excellent example of a successful detection by our highly trained staff."
A spokesman said the driver and haulier may be liable for a fine if they cannot prove they took adequate steps to secure the load which was stopped at 6.20am on June 30.
