Boko Haram militants have released dozens of girls out of a group of more than 200 who they kidnapped from the northeastern town of Chibok in April 2014, officials said on Saturday.
About 220 girls were abducted from their school in Chibok in a night-time attack in 2014. Prior to this release, 195 were believed to be still in the captivity.
A government minister, asking not to be named, said 82 girls had been released. But unconfirmed reports on social media put the number of freed girls at between 50 and 62.
"The girls were released through negotiations with the government," one official said, asking not to be named, adding that an official statement would follow shortly.
A military source said the girls were currently in Banki near the Cameroon border for a medical check before they will be airlifted to Maiduguri, the capital of Borno state.
Negotiations on kidnapped girls
Nigerian President Muhammadu Buhari said last month the government was in talks to secure the release of the remaining captives.
Last October, more than 20 girls were released in a deal brokered by the International Committee of the Red Cross.
Others have escaped or been rescued.
The Chibok girls have sparked a global campaign dubbed #bringbackourgirls supported by then US First Lady Michelle Obama and a list of celebrities.
Although the Chibok girls are the most high-profile case, Boko Haram has kidnapped thousands of adults and children, many of whose cases have been neglected.
The militants have killed more than 20,000 people and displaced more than 2 million during its eight-year insurgency.
Despite the army saying the insurgency is on the run, large parts of the northeast, particularly in Borno state, remain under threat from the militants.
Suicide bombings and gun attacks have increased in the region since the end of the rainy season late last year.