Nigeria has claimed the rescue of a second Chibok girl, just days after the first, but campaigners on Friday cast doubt on her identity and attention turned to the circumstances of the releases.
The army said Serah Luka was among 97 women and children rescued in the Damboa area of northeast Nigeria on Thursday morning during military operations against Boko Haram Islamists.
The announcement came just hours after the first girl to be found, Amina Ali, met President Muhammadu Buhari, who said the discovery gave a "unique opportunity" to find the remaining hostages.
The 19-year-old was discovered with her four-month-old baby girl, Safiya, and a man she described as her husband near Boko Haram's Sambisa Forest enclave on Tuesday.
Nigeria's military, which has pushed out Boko Haram from captured territory in the last 15 months, has been conducting operations in the former game reserve in Borno state since late April.
Until this week, rebel fighters held 219 of the 276 students abducted from the Government Girls Secondary School in the remote town of Chibok on the evening of April 14, 2014.
Fifty-seven escaped in the immediate aftermath of the kidnapping, which provoked global outrage and brought unprecedented attention on the conflict, which has killed at least 20,000 since 2009.
The head of the Abducted Chibok Girls Parents group, Yakubu Nkeki, said unlike the first announcement about Amina, the military had not contacted them beforehand to establish the second girl's identity.
Only two girls with the surname Luka were on the list of abducted girls and none was from Madagali, in neighbouring Adamawa state, as the military said the second student had claimed, he added.
The military said the teenager was believed to be a Christian pastor's daughter but Nkeki said there were only four priests on the list of parents and none was called Luka.
"I can say in my capacity as the head of the Chibok Abducted Girls Parents group that this girl is not among the abducted Chibok girls," he told AFP.
The head of the BringBackOurGirls campaign group in Abuja, Oby Ezekwisili, said they were "overjoyed" at the rescue but tweeted: "We have asked for some further verification of her identity." A senior military source stood by the army's statement, saying it was "beyond reasonable doubt" that she was among the girls snatched.
"The military personnel who carried out the rescue operation and the civilian vigilantes who assisted them and those who know the girl confirmed that she is among those abducted," he added.
"We can only change our position if the principal of the school or the government of Borno state come out and refute this established identity of the girl." This week's developments have raised hopes that the remaining students will be released and follows a so-called "proof of life" video sent to the government earlier this year.
Until then, none of the kidnapped schoolgirls had been seen since May 2014, when they were shown in a Boko Haram video, apparently converted to Islam and reciting passages from the Quran.
Nigeria's government was cautious about the "proof of life" video because of difficulties establishing whether those who sent it had the authority of the group's leadership to request talks.
Security analysts tracking the conflict suggested Amina may have been released as a gesture of "good faith" by Boko Haram elements rather than by simply military action.
Ryan Cummings, from Signal Risk, said escape was unlikely given that the Chibok girls were said to have been heavily guarded at militant camps in the Sambisa Forest, a vast semi-desert scrubland.
"It seems very fortuitous that the hostage (Amina), child and BH husband just happened to run into a CJTF (civilian joint taskforce) patrol as described", he told AFP in an email.
Nigeria's military have described the man found with Amina as a "suspected Boko Haram terrorist".
Cummings also suggested reports of his "defection" with such a prized asset, straight into the hands of the Nigerian army and military intelligence, also seemed unlikely.