The release reportedly came after talks with the government, though few details are confirmed.
The abduction of the so-called "Chibok girls" triggered a global outcry and sparked a huge social media campaign.
Before the latest release, about 195 of the girls were still missing. The number of girls in the latest release is unconfirmed, and varies from about 50 to 80.
The Sahara Reporters website quoted a source as saying the freed girls were now in the town of Banki in Borno state, awaiting an airlift.
They would be taken to a secure location, the source said, for debriefing and would then be reunited with their families.
After the abduction in 2014, a number of girls escaped and Boko Haram then freed 21 last October, after negotiations with the Red Cross.
Last month, President Muhammadu Buhari said the government remained "in constant touch through negotiations, through local intelligence to secure the release of the remaining girls and other abducted persons unharmed".
Many of the Chibok girls were Christian, but were encouraged to convert to Islam and to marry their kidnappers during their time in captivity. (source: bbc.com)