The rescued migrants, including two children were treated in hospital for "mild hypothermia".
Eight migrants, including two children, have been found with hypothermia in a refrigerated truck at the cross-Channel port of Calais, the AFP news agency said.
The rescued migrants, who say they are from Afghanistan, were found during an inspection of the truck before it was loaded on a ferry to Britain, according to the public prosecutor's office in Boulogne-sur-Mer.
The fire brigade said the group was treated for "mild hypothermia" and taken to hospital.
Two Romanian drivers of the truck were taken into custody.
Essex truck deaths
The Calais discovery came days after the bodies of 39 people were found in a truck in Essex, UK.
Essex Police originally said those found in the lorry were "believed to be Chinese nationals", but after the Vietnamese Embassy in London said it had received calls from citizens fearing they had relatives on the truck, the force said that they could not "realistically speculate" on the nationality of the victims.
Three men have been released on bail, after questioning over the incident, while 25-year-old Maurice Robinson will appear in court on Monday, charged with "conspiracy to traffic people, conspiracy to assist unlawful immigration, and money laundering".