Police said nearly 500 boys and men were rescued from a "torture house" where they were chained, abused and enslaved.
Some boys and men have been detained for many years. Some victims were only about 5 years old. They are tortured, sexually abused and starved if they seek to escape. Many children have metal holes around their ankles and many large wounds.
The police said that 8 people were arrested and all were teachers.
Some children reported to the police that their relatives took them to the building because they thought it was a Koran school. Police said there were signs that they were being propagandized.
Bello Hamza, 42, a victim who was held hastily for three months, told the press: "This place looks like an Hoi giao hotpot, but anyone who tries to escape here will be severely punished. They tie and hang people up on the ceiling to punish them, but if they participate in same-sex sex, they will not be punished. During the short time I was here, someone died from torture. Others died before me due to poor health and were tortured."
According to Bello, the people in this building are given a very poor diet with 2 meals a day, at 11am and 10pm.
Among the victims here, in addition to the Nigerals, there are also people from Burkina Faso and Mali.
Police chief Ali Janga told the BBC that the house was raided after reports of suspicious activities.
