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Chief investigator of Mexico mass killings goes missing

28 August 2010 Last updated at 05:11 BST

Mexican prosecutors say they are deeply concerned for the safety of a detective who is leading an investigation into the killing of 72 foreign migrants.

The wife of Roberto Suarez told the BBC he had been missing since Wednesday, the day after the migrants were found dead at a ranch in Tamaulipas state.

A police officer who was travelling with him has also disappeared. Sebastian Usher reports.