The children, who were abducted from a Catholic school in the town of Papiri in Niger state last month, are expected to be handed over to authorities on Monday.
The fate of another 165 students and school staff who remain in the hands of the kidnappers is unclear.
A total of 315 people were taken away from the school in November. Around 50 have managed to escape.
What preceded – for example, negotiations or military pressure – the 100 children being released is unclear.
Mass kidnappings are a recurring occurrence in Nigeria. For criminal and armed groups, it can be a way to obtain significant ransoms.
