Lawal Ahmad, a 33-year-old who was held captive, said he witnessed sexual assault, beatings and the death of other captives during his two years there.
Police in Nigeria are trying to reunite dozens of men and boys with their families this week after rescuing them from an Islamic school where they had been "shackled with chains" and subjected to "various inhuman and degrading treatments", according to reports.
Police said the school's proprietor, 78-year old Bello Mai Almajirai, "has been in the business for more than 40 years and now he has become old he no longer has the capacity to run the rehab Islamic school".
"We learnt that the inmates here are over 300 and because of the inhuman treatments they are being subjected to they revolted yesterday", Katsina police spokesman Sanusi Buba told reporters on Monday.
The centre is being operated by one Malam Bello in Daura town and had reportedly been in existence for decades.
The commissioner said when policemen stormed the place, they discovered six rooms with over 40 inmates each dehumanised and chained.
Nigerian President, Muhammadu Buhari is a native of Daura.
Umar said Bello was among the leading Imams in the area and wondered why such activities could take place within an Islamic school, urging the police not to leave any stone unturned in bringing those involved in the inhuman treatment of the victims to book. "If you are studying they will beat you". "So, I think it was yesterday (Sunday) that they revolted and started escaping from this facility". I will meet with the Emir of Daura and Governor Aminu Masari on the issue. Some parents do take their children to religious centres when they engaged in any kind of misbehaviours which include drug addiction and stealing.
The place was discovered after some of the boys who had escaped embarked on a protest over allegations of violation of human rights at the centre.