Officers rescued four people from the back of a lorry prompting a fresh plea for people to be vigilant on the roads and report anything suspicious.
Police near Cambridge received a call for help from one of the four people inside the vehicle that had entered the country at Dover.
The lorry was stopped just before junction 11 of the M11 near Trumpington on Saturday just after noon.
Those rescued from inside were not injured and their welfare is now being handled by the immigration services.
The driver was arrested on suspicion of assisting illegal entry into the UK, but has since been interviewed and will face no further action.
Cambridgeshire Police said: “News of the weekend lorry rescue follows two similar incidents last month, where 21 people were rescued from lorries in Cambridgeshire.
“Some had told officers over the phone that they were struggling to breathe.
“Stories like this may be distressing, but highlight that slavery and trafficking still exist and police need the public’s help.”
Anyone who sees people emerging from a lorry is urged to call police on 999 immediately and take a note of the vehicle registration number, even if it has foreign plates.
Read more: All the latest news from Dover