Abuja - Themilitary is conducting a round-the-clock search operation to locate more than 200 schoolgirls abducted by Boko Haram militants, the defence spokesman said on Friday.
Chris Olukolade said two divisions of the army were trying to track down the girls and were operating in the far north along the frontier with Niger, Chad and Cameroon while border guards were on high alert.
The air force had already flown more than 250 sorties in possible areas where the girls are being held within Nigeria, he told a news conference in the capital, Abuja.
"The major challenge remains the fact that some of the information given here turned out in many occasions to be misleading and to be exhausting of the search teams," Olukolade said.
"Nevertheless, this will not discourage the collaborative efforts that are on-going."
International outrage has grown since 276 girls were abducted from the remote northeastern town of Chibok on April 14 and has since led to offers of support from a number of countries.
US, British and French teams arrived in Abuja on Friday as part of the search effort to find the 223 that are still missing.
Olukolade said that surveillance equipment was sent to the region two days ago to help at least 10 separate search teams.
Troops from Chad and Niger serving as part of the joint task force in the restive northeast were also involved and had been asked to keep in touch with their commanders to track any possible movements in their countries, he added.