Forty-one migrants were found alive in a refrigerated truck in northern Greece on Monday, said police, who arrested the driver.
The migrants, of apparent Afghan origin, were mostly in good condition. Seven of them were given first aid in hospital, the police said.
"The truck contained men and boys. Identifying their nationality will require a couple of days," a police source told AFP.
The truck was immobilised by police on the Egnatia motorway between the towns of Xanthi and Komotini.
The driver, a man from Georgia, was arrested.
The discovery came after 39 people, all believed to be Vietnamese nationals, were found dead in a refrigerated truck in Britain last month, highlighting the risks of illegal migrant routes to Europe, even for those avoiding perilous travel by sea.
Another 31 Pakistani migrants were found on Saturday hidden in a lorry on a motorway near the French-Italian border.