The truck had been carrying 31 people, reportedly from Pakistan, when it was inspected by authorities in southern France. The latest discovery comes after dozens of migrants were found dead in a truck near London.
Officers carrying out a routine traffic check in southern France uncovered dozens of migrants in the back of a truck on Saturday, the public prosecutor's office in Nice said.
Some 31 people, including three unaccompanied minors, were found in the truck during a vehicle spot-check at a toll booth near La Turbie, near the border with Italy.
Prosecutors said that all 31 people on board were Pakistani nationals. The driver of the truck, who is also from Pakistan, was arrested by French authorities.
The migrants were handed over to Italian authorities, the Nice-Matin newspaper reported.
Prosecutors will now try to determine whether a human smuggling ring is behind the operation. Should that prove not to be the case, the driver of the truck will be charged with aiding and abetting illegal immigration, news agency AFP reported.
Concerns after UK migrant truck deaths
The discovery comes just days after French authorities in the northern port city of Calais pulled over a refrigerated truck carrying eight migrants. All those inside the truck, including four children, were taken to the hospital after exhibiting signs of hypothermia.
Border control agencies have been on high alert following the deaths of 39 migrants in the UK on October 23.
The migrants, who were determined to be Vietnamese nationals, had also been transported in a refrigerated truck when the vehicle was found east of London.
The alleged driver of the truck, a 25-year-old from Northern Ireland, has already been charged over the deaths. He faces 39 counts of manslaughter as well as human trafficking and immigration offenses.