Investigators discovered 29 stowaways hidden inside three lorries in northern France waiting to cross to the UK, the Border Force said.
The first group of 19 - 12 from Iran and seven from Vietnam - were found when officers in Dunkirk searched a Latvian-registered lorry en-route to Dublin.
The Latvian driver was handed over for questioning to the French Border Police on suspicion of attempted facilitation following the discovery in the early hours of Friday.
The people found inside the truck - two women and 17 men - were also handed to the French authorities as further investigations are carried out.
Today, another group of five stowaways was found by officers using sniffer dogs at Dunkirk in a Romanian-registered vehicle heading for Loughborough, Leicestershire.
At Calais on Friday five men from Afghanistan were found by a sniffer dog hiding in a Polish-registered lorry at the port of Calais bound for Northampton.
Both of these groups were handed to the French Border Police and the vehicles allowed to continue.
Carole Upshall, the Border Force director for South and Europe, said: "These incidents show why we base Border Force staff in France - to stop would-be illegal immigrants before they can reach the UK.
"Our strong presence in French ports like Dunkirk and Calais helps protect the whole of the UK from people attempting to enter the country illegally.
"Our officers use sniffer dogs, heartbeat detectors and carbon dioxide probes as well as physical searches to find people hiding in vehicles."