The Nigerian government said the released girls were in state custody.
Maiduguri has been at the epicenter of the group's seven-year insurgency.
No group has yet claimed responsibility for the attack.
The Nigerian military said it had "fatally wounded" Shekau in August.
Aliko Dangote, a Nigerian cement magnate, is a big fan of the London club.
Abubakar Shekau, the group's leader, does not appear in the Eid video.
Ahmad Salkida was accused by the Nigerian military of concealing information about the whereabouts of the Chibok girls.
The Nigerian military is planning a large offensive on the group's final stronghold in the near future.
Kerry visited the country's top Islamic leader and met with northern governors during his visit.
Shekau recently rejected ISIS's recent announcement of a new Boko Haram leader.
Amina Ali Nkeki escaped in May and fathered a child by a suspected Boko Haram member.
The militant group's latest video demanded the release of its fighters in exchange for the girls.
One of the Nigerian schoolgirls is used to plead with the federal government to release Boko Haram militants.
Economics, not ideology, is the driving force behind Nigeria's Islamist insurgency.
A purported ISIS magazine has designated Abu Musab al-Barnawi as the Nigerian group's new chief.
A quarter of a million children are suffering from malnutrition in the militants' wake, UNICEF said.
Power was visiting West Africa to meet Boko Haram victims.