The girls went missing after jihadists stormed their school in the town of Dapchi in the north-eastern Yobe state on 19 February.
President Muhammadu Buhari said it was a “national disaster” and apologised to the girls’ families.
The attack has revived memories of the Chibok schoolgirl abduction in 2014.
Anger has been growing among the girls’ parents amid reports that soldiers had been withdrawn from key checkpoints in Dapchi last month.
Dapchi, which is about 275km (170 miles) north-west of Chibok, came under attack last Monday, causing students and teachers from the Government Girls Science and Technical College to flee into the surrounding bush.
Residents say that Nigeria’s security forces, backed by military jets, later repelled the attack.
Authorities initially denied the students had been kidnapped, saying they were hiding from their attackers.
But they later admitted that 110 girls were missing after the attack.
Boko Haram militants have been fighting a long insurgency in the country’s north in their quest for an Islamic state in the region.
Nearly four years ago they abducted 276 girls from a school in Chibok, leading to a worldwide #BringBackOurGirls campaign. The location of more than 100 of those girls is still unknown.
The conflict is estimated to have killed tens of thousands of people, and led to the abduction of thousands. (Courtesy BBC)