Herrera said that the investigation refers to the period between 2009 and 2012 when the Zetas had near complete control of the prison near the city of Piedras Negras, just over the border from Eagle Pass in Texas.
He said this week’s arrests for the atrocities allegedly committed in the prison relate to the cases of the first seven disappeared people who investigators believe they have confirmed were among the victims. That proof, however, relies primarily on information from dozens of interviews with imprisoned witnesses and some of those involved, rather than on physical evidence.
According to José Juan Morales, spokesman for the investigation, the Zetas were allowed to leave the Piedras Negras prison at night to kidnap their victims, sometimes wearing fake police and army uniforms.
The remains of those killed were then, the investigation found, dumped in the nearby San Rodrigo river and in the Rio Bravo estuary.