Kidnapped Nigerian girls have likely been split up, and may have been moved into other countries. 

But the task of recovering the girls appeared to grow more complicated with news that U.S. intelligence believe the 276 girls have been split up. "We do think they have been broken up into smaller groups," U.S. Navy Rear Adm. John Kirby, the Pentagon press secretary, said. He declined to detail how U.S. officials came to the conclusion.

It is a sentiment that has been echoed by a number of others, who believe the girls already have been moved out of Nigeria and into neighboring countries. "The search must be in Niger, Cameroon and Chad, to see if we can find information," former UK Prime Minister Gordon Brown, the U.N.'s special envoy for global education, told CNN.