Around 100 children who were kidnapped from a Catholic school in Nigeria have been released, according to local authorities.

Up to 315 pupils and staff were abducted from St. Mary’s Catholic School in Papiri, Niger State, in November. According to the Christian Association of Nigeria, it was one of the worst mass kidnappings the country has ever seen.

Fifty students managed to escape in the hours after the abduction. The condition of the remaining missing pupils remains unclear.

Bishop Bulus Dauwa Yohanna, who is in charge of the boarding school, confirmed the release to the BBC but said he did not know the children’s current location.

It may take time for a formal handover to happen as authorities process and offer support to the children, according to the bishop. A time for the students to be reunited with their parents has not yet been set.

No further details about how the release was secured have been revealed. The governor of nearby Nasarawa State told local media that behind-the-scenes work by the federal government could not be publicized for security reasons.

Bishop Bulus called the mass abduction “a profound moral and spiritual wound to the community and to humanity,” telling Nigeria's national security advisor that parents fear for the lives of their children.

No group has claimed responsibility for the abductions. Churches and schools have repeatedly been targeted by jihadist groups in central and northern Nigeria.

U.S. President Donald Trump has said there is a “Christian genocide” taking place in the country, a claim rejected by its government.