Army spokesman Colonel Sani Usman "has confirmed the rescue of another Chibok girl this evening", a statement said yesterday, without giving further details.
The first of the 219 abducted students, Amina Ali, was found on Tuesday by troops and civilian vigilantes near Boko Haram's stronghold in the Sambisa Forest area of Borno state, northeast Nigeria.
The 19-year-old and her mother met President Muhammadu Buhari at his official residence in Abuja earlier yesterday, where the head of state said the government was "doing all it can to rescue the remaining Chibok girls".
Amina was quoted as saying by a campaign group pushing for the girls' release that all the students were still being held in the former game reserve, where the Islamists have had camps, but that six had died.
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Nigeria's military has been mounting an offensive in the sprawling, semi-desert scrubland since late April to flush out rebel fighters.
Boko Haram is thought to have kidnapped thousands of women and young girls since the start of its insurgency to create a hardline Islamic state.
The Chibok kidnapping saw 276 seized from their school in the remote town on April 14, 2014. Fifty-seven escaped soon in the immediate aftermath.