The Nigerian army says it has freed 97 women and girls from Boko Haram, including one of the more than 200 girls abducted from Chibok school.
However, Chibok campaigners say that while the girl in question was a pupil at the school, she was actually kidnapped from her home elsewhere.
This comes days after the first of the Chibok girls was freed.
The Islamist militant group has seized thousands of women and girls in northern Nigeria, rights groups say.
But it was the abduction of the girls from Chibok that gained international attention through the #BringBackOurGirls campaign, which was supported by US First Lady Michelle Obama and Pakistani activist Malala Yousafzai.
The army has made several mistakes in its statements about the Chibok girls - in its initial statement after the first girl was found on Wednesday, it used the wrong name.
It has claimed to have freed more than 100 of them before later backtracking.
In all, 218 girls remain missing since they were seized from Chibok secondary school in Borno state, north-eastern Nigeria, in April 2014.
The girl rescued earlier this week told a Chibok community leader that six of the kidnapped girls had died but the rest were still in the Sambisa forest where she was found.
Behind the headlines: Tomi Oladipo, BBC Africa Security Correspondent
It would have been ideal for the Nigerian army to rescue two of the Chibok girls in three days - only it did not happen, despite the speed and enthusiasm with which the press statements were sent out.
The military has been trying to win over the public following heavy criticism it has received for its inability to bring back the schoolgirls. Such has been its focus that it has not capitalised on the work of its troops in rescuing thousands of Boko Haram captives.
In fact, army records show it freed 11,595 people between February and April this year. That has barely been publicised - although the abductions of those people also did not make headlines, unlike the schoolgirls whose disappearance raised concern around the world.
As important as the Chibok girls are, it appears their fate is being used as a measure of success in the fight against Boko Haram.
In a statement, army spokesman Col Sani Usman said the 97 women and girls had been found on Thursday in the Demboa area of Borno, during an operation in which 35 militants were killed.
"Among those rescued is a girl believed to be one of the Chibok Government Secondary School girls that were abducted on 14 April 2014," he said.
However, the BringBackOurGirls group said it had established that the rescued girl had been abducted from her home in Madagali, in neighbouring Adamawa state.
Earlier on Thursday, the first Chibok girl found was flown to the capital Abuja to meet President Muhammadu Buhari.
Mr Buhari said he was delighted she was back and vowed to help her resume her education.
"But my feelings are tinged with deep sadness at the horrors the young girl has had to go through at such an early stage in her life," he added.
She was found by an army-backed vigilante group in the huge Sambisa Forest, close to the border with Cameroon, along with her four-month-old baby.
She was with a suspected member of Boko Haram who claimed to be her husband.
More on the Chibok abductions:
During the April 2014 attack, Boko Haram gunmen arrived in Chibok at night and raided the school dormitories, loading 276 girls on to trucks.
More than 50 managed to escape within hours, mostly by jumping off the lorries and running into roadside bushes, leaving 219 in the hand of Boko Haram.
Boko Haram at a glance:
- Founded in 2002, initially focused on opposing Western-style education - Boko Haram means "Western education is forbidden" in the Hausa language
- Launched military operations in 2009
- Thousands killed, mostly in north-eastern Nigeria, and hundreds abducted
- Joined so-called Islamic State, now calls itself IS's "West African province"
- Seized large area in north-east, where it declared caliphate
- Regional force has now retaken most of that territory