The Nigerian military is joining the search for at least 100 teenage girls abducted from a school in the remote northeast.
It is thought that Islamist militant group Boko Haram took them to a forest near the Cameroonian border.
The air force, army, police and local volunteers are all involved in the search, officials say.
For years, Boko Haram has been waging a bloody armed campaign for an Islamic state in northern Nigeria.
The militant group’s name means “Western education is forbidden” in the local Hausa language.
The BBC’s Hausa Service says the group has kidnapped civilians in the past – usually women to work as sex slaves.
Gunmen reportedly arrived at the school in Chibok, a remote area of Borno state, late on Tuesday, and ordered its teenage residents on to lorries.
A local politician said about 50 army soldiers had been stationed near the school ahead of annual exams, but were apparently overpowered.
Local residents reported hearing explosions followed by gunfire.
“Many girls were abducted by the rampaging gunmen who stormed the school in a convoy of vehicles,” local education official Emmanuel Sam told the AFP news agency.