Nigerian authorities are searching for the families of 105 abducted children found packed into a minibus.
The children, aged between five and 13, were taken from Kano state in the north and, say anti-trafficking agents, would have been "abused and molested".
Police found the children crammed into a 15-seat bus in the northern city of Kaduna on Thursday after the driver was stopped at a police checkpoint.
The children were piled on top of each other "like sardines" say officials.
It is the largest number of trafficked children the authorities have rescued in one incident since efforts began to stop the trade in 2003.
Three men arrested with the children said they were taking them to a school in Suleja, 400kms away in Niger state, to learn the Koran.
But officials doubt the story as there are plenty of legitimate Islamic schools in Kano, they say.
The children have been taken to a shelter where they have been given food, clothes and a medical check.
The police and agents from the National Agency for the Prohibition of Traffic in Persons (Naptip) have taken the arrested men to the area they claim the children are from to find their parents.
"It would have been very easy for these people to drive around communities harvesting children. It may also be their parents are complicit in this. The fact is that once these children are taken out of their communities they will be devoured by wicked people, abused and molested," said Naptip spokesman Orakwue Arinze.
Under the traditional Islamic Almajiri school system, children are sent away to learn the Koran by their parents. But many end up begging on the roads and are exploited by their "teachers".
Islamic leaders have called for the system to be reformed.
"The Almajiri system is not doing a good things for Islam and Muslims and to Nigeria. It has a negative effect on our human development and the economic progress of the country," Kano-based Imam Sani Isa said.
He called on poor families to have fewer children. "If you can't afford to clothe, feed and educate your children than you are hiding from your responsibilities -it's a sin," he said.