Mexican official defends evidence in students' case

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The director of Mexico's criminal investigation agency is defending the handling of evidence in the case of 43 missing students, after an international group of experts raised questions about it.

Tomas Zeron says he visited the scene where charred bone fragments believed to belong to the students were found on Oct. 29, 2014. He acknowledges that he visited the scene Oct. 28, but he said Wednesday no evidence was picked up that day.

The group of outside experts had questioned why an investigator was seen picking up a bone earlier, and at a different site, than investigative records suggest.

Zeron said the bone belonged to a bird.

The experts and the victims' parents question the government's version that the students were killed, burned and their bones dumped in a river.