The Religious School, which also served as a rehabilitation center, was run the following day by a 78-year-old Muslim cleric in Daura, the birthplace of Nigerian President Muhammadu Buhari.
The authorities visited the school on Monday after students protested against their welfare and gave the police an indication of the conditions in the facility, said Isah Gambo, police spokesman in Katsina, told CNN.
The students, aged between 7 and 40 years, said they were denied food for days and chained by the school's teachers, Gambo said.
Others also said that they had been abused and sexually abused during their stay at school.
Some of them said they were beaten almost every morning when they saw their stomach and some parts of their bodies. There were so many foxing spots. They did not get food in time, the shelter was inadequate, and some said they had been sexually abused, "Gambo told police CNN, Gambo said.
"Parents bring their unruly children to these schools to rehabilitate themselves and learn the Koran because they have no other option, but that's no excuse for violating their rights," said Gambo.