ol in Chibok, located on the fringes of Sambisa Forest, loading scores of schoolgirls onto trucks before driving away unchallenged.In a 17-minute video last week, Boko Haram leader Abubakar Shekau offered to exchange the kidnapped girls for Boko Haram militants held by Nigerian authorities.At least four countries, including the U.S. and Britain, are currently assisting in search and rescue efforts