The released group included 27 students, teachers and family members, the state government said in a statement at the time of the abduction.
The armies, wearing military uniforms according to witnesses, stormed the Kagara government science school on February 17. One student who died during the attack was named Benjamin Habila.
Niger State Executive Governor Abubakar Sani Bello wrote on Twitter that those released were received by the state government.
This comes at a time when hundreds of schoolgirls were abducted in the early hours of Friday, when gunmen attacked a state-run school in Zamfara state, northwestern Nigeria.
The schools were taken from their homes by gunmen who raided the government girls’ high school in Jangebe, a senior government official who knew about the incident told CNN.