British police rescued 15 illegal Afghan migrants after a seven-year-old boy texted a volunteer for assistance from inside a sealed lorry, media reports said.
Seven-year-old Ahmed used a mobile phone he had received from a British aid worker in a French migrant camp to inform the aid worker they were running out of oxygen.
Inca Sorrell, who was attending a conference in New York when she was sent the SMS, contacted a colleague in Britain, Tanya Freedman, the BBC said.
Freedman, a worker with the British organisation called Help Refugees, passed the message on to the relevant officers, who traced the phone and stopped the truck.
Police said one man had been detained on suspicion of assisting illegal immigration. Freedman said: "The boy was in a very dangerous situation. Some lives have been saved today."
Ahmad had been living in the Calais camp known as the Jungle. He regularly visited women and children's centre in Calais and was often alone. He is in the care of social services.