Police say they rescued eight people from a lorry travelling on the A14 on Thursday evening after receiving a call from someone in the back of the vehicle.
The HGV was stopped at about 7.15pm near Spaldwick.
A man who was inside the vehicle was taken to hospital, but was not seriously injured. No other injuries were reported.
A spokesman for Cambridgeshire police said a man has been arrested on suspicion of assisting unlawful immigration.
The spokesman added: "The investigation and welfare of the people involved has been handed to the immigration services."