A Nigerian journalist with links to the Islamist group Boko Haram has claimed only 15 out of the 112 missing Chibok girls are still alive.
The 276 schoolgirls were abducted by Boko Haram exactly four years ago.
Many have since been released.
Ahmad Salkida said he had negotiated for the girls' release on behalf of the government, but several opportunities to have them freed had been missed.
The Nigerian government said there was no reason to think some may be dead.
A spokesperson told the BBC the government was still in discussions with Boko Haram to secure the release of the 112 girls who remain missing.