BOKO HARAM MAY RELEASE CHIBOK GIRLS...

Nigerian presidential aide Hassan Tukur told BBC Focus on Africa that the cease-fire agreement came after months of negotiations mediated by Chad.

The girls were kidnapped by Boko Haram — the group's nickname means "education is sinful" — on April 15 while in school in the northeastern town of Chibok.

"They've assured us they have the girls, and they will release them," Tukur told the BBC."I am cautiously optimistic."

Talking to CNN, Tukur said, "We have agreed on the release of the Chibok schoolgirls, and we expect to conclude on that at our next meeting with the group's representative next week in Chad."

Voice of America reported Tukur and Danladi Ahmadu, who calls himself the secretary-general of the militant group, said the girls would be released. The release was set to happen Monday in Chad, according to VOA's Hausa-language service.

Maj. Gen. Chris Olukolade, a Nigerian Defense Ministry spokesman, told the Associated Press the girls' release is still being negotiated.

Boko Haram negotiators "assured that the schoolgirls and all other people in their captivity are all alive and well," Mike Omeri, the government spokesman on the insurgency, told a news conference after the truce was announced.