Authorities in Nigeria say some of the schoolgirls who were reportedly abducted since their school was attacked by Boko Haram militants earlier this week have been rescued.

The missing schoolgirls were discovered at a border town between the states of the Yobe and Borno Wednesday, two days after armed gunmen stormed the Government Girls Science Secondary School in the town of Dapchi in the northeastern state of Yobe.

People with direct knowledge of the matter said 91 students were found to be absent after a Tuesday roll-call at the school.

The disappearance has raised fears of another mass kidnapping by Boko Haram, which abducted 276 girls from a school in the village of Chibok in April 2014.

That abduction sparked a worldwide outrage and triggered formation of the Bring Back Our Girls movement. Nearly four years later, more than 100 of the Chibok girls are still missing.