Chibok girls

As the Chibok girls waited patiently Wednesday to meet the man who signed off on their release -- Nigerian President Muhammadu Buhari -- it was remarkable to see the physical transformation from emaciated and haggard looking former hostages to seemingly carefree and happy young women.

The faded and torn clothes they arrived in have since been replaced with tailored and brightly colored fabrics that concealed their still painfully-thin frames.

CNN reports this from two sources with direct knowledge of the negotiations.

That's because the rest -- about 114 -- have either died, been married off, or become radicalized and don't want to leave their Boko Haram kidnappers, the sources said.

Negotiations between Boko Haram and the Nigerian government over the captives are expected to resume Monday, four days after the militant group handed over 21 former Chibok schoolgirls to authorities in northeastern Nigeria.

In an emotional ceremony in the capital Abuja, one of the girls said they had survived for 40 days without food and narrowly escaped death at least once.

It is unclear how the release was negotiated, but an official says talks are under way to free some more girls.

Of the 276 students kidnapped in April 2014, 197 are still missing.

One of the girls freed said during a Christian ceremony in Abuja: "I was... [in] the woods when the plane dropped a bomb near me but I wasn't hurt.