The released group consisted of 27 students, teachers and family members, the state government said in a statement at the time of the kidnapping.
The gunmen, who, according to witnesses, were wearing military clothing, stormed the Government Science Secondary School Kagara on February 17. One student who died in the attack was named Benjamin Habila.
The executive governor of the state of Niger, Abubakar Sani Bello, tweeted that those released have been received by the state government.
This is because hundreds of schoolgirls were kidnapped in the early hours of Friday when gunmen raided a state school in Zamfara state, northwestern Nigeria.
The schoolgirls were taken from their hostels by gunmen who raided the Government Girls Secondary School in the town of Jangebe, a senior government official with knowledge of the incident told CNN.