Nigeria's military has admitted that most of the teenage girls abducted by suspected Islamist militants have not been freed as it earlier stated.
There has been confusion about the number of girls missing after they were kidnapped from a boarding school in the north-east on Monday night.
According to education authorities in Borno state, 99 girls are still missing and 30 in total have managed to escape.
Intensive efforts to find them are continuing, an army spokesman said.
The security forces were working with vigilante groups and local hunters to track the schoolgirls, Chris Olukolade said in a statement.
It is thought Islamist militant group Boko Haram took the girls to forested areas near the Cameroonian border.
Correspondents say the raid on the boarding school is a great source of embarrassment for the Nigerian authorities, who have been saying that their military campaign against the militants is succeeding.
'No intention to deceive'
The attack on the school in Chibok, a remote part of Borno state, happened late on Monday with gunmen reportedly storming the school, stealing food supplies and ordering the students onto lorries.
On Wednesday, the military said most of the abducted students had been freed "as troops pursuing the terrorists close in on the den of those believed to have carried out the attack".
But Mr Olukolade said it was based on a report "filed in from the field indicating that a major breakthrough had been recorded in the search".
"The report forwarded to the public on this issue was in good faith and not intended to deceive the public," he said.
"The number of those still missing is not the issue now as the life of every Nigerian is very precious."
On Thursday, a group of parents headed off into the Sambisa forest in a desperate search for their daughters.
It is an extremely dangerous mission, the BBC's Nigeria correspondent Will Ross reports.
The well-armed Boko Haram fighters have killed hundreds of civilians this year, slitting the throats of many of their victims, he says.
Borno, Yobe and Adamawa states in north-east Nigeria have been under emergency rule since last May.
Militants from Boko Haram - which means "Western education is forbidden" in the local Hausa language - frequently target educational institutions.