Some 132 prisoners have escaped from a northern Mexico prison close to the US border, setting off a massive manhunt. The director and two workers at the Piedras Negras institution have been detained in an investigation into the prison break just across the border from Eagle Pass, Texas. Nearly 90 of the prisoners were serving time or facing trial on federal charges, such as drug trafficking. Mexican army convoys are patrolling the area, and officials are offering rewards of up to $15,000 for information leading to the arrest of each prisoner, AP reports. (More Texas stories.)