The official spoke on condition of anonymity late yesterday because they were not authorised to speak to reporters.
Nearly 200 of the schoolgirls had remained captive before this release.
Many of the girls seized from their boarding school were forced into marriages with fighters and became pregnant.
Nigeria's government in October announced the first negotiated release of 21 of the schoolgirls.
At the time, it said another group of 83 girls would be released "very soon."
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