Abuja - A campaign group on Friday said an abducted schoolgirl rescued from Boko Haram was a student in Chibok but was not among the 219 seized more than two years ago.
Nigeria's military announced late on Thursday that Serah Luka was among 97 women and children rescued earlier that day in the Damboa area of the northeastern state of Borno.
But the head of the Chibok Abducted Girls Parents group, Yakubu Nkeki, said she was not on the list of 219 girls held by the militants since the mass abduction on April 14, 2014.
A senior military source maintained it was "beyond reasonable doubt" that the schoolgirl was one of them.
But BringBackOurGirls spokesman Sesugh Akume said background checks with a community leader in Chibok had established that although Serah was a student at the same school, she was in a different class.
"She was an SSS1 learner at (Government Girls Secondary School) Chibok, who was abducted by the insurgents in her home in Madagali (in neighbouring Adamawa state)," he added.
SSS1 is the first year of the final three years of secondary school in the Nigerian system. The 219 girls held were in the final year, SSS3.
News of the rescue came just hours after the first student to be found, Amina Ali, met President Muhammadu Buhari in the capital, Abuja.
Boko Haram has kidnapped thousands of women and young girls since the start of the conflict in 2009, which has left at least 20 000 dead and made more than 2.6 million others homeless.
BringBackOurGirls, which has campaigned for the release of all hostages, said: "Every citizen returned is victory for us all."