More than 130 inmates escaped through a tunnel from a prison in northern Mexico on Monday, setting off a massive search by police and soldiers in an area close to the US border.
Authorities in Coahuila state said the 132 inmates fled the prison in Piedras Negras, a city across the border from Eagle Pass, Texas, through a tunnel that was 21ft long and 4ft in diameter, then cut their way through a chain link barrier and escaped on to a neighbouring property.
The Coahuila attorney general Homero Ramos Gloria, said the director and two other employees of the state prison had been detained pending an investigation and were being questioned by authorities about their possible involvement. The prison houses about 730 inmates.
The tunnel "was not made today", Ramos told the Milenio TV station. "It had been there for months."
He added: "The prison was not overcrowded. None of our prisons are. We have 132 inmates escaping through a tunnel, and it doesn't make sense."
Authorities said they found ropes and electric cables they believed were used in the break. Federal police units and Mexican troops were deployed to search for the missing inmates, while rewards of up to $15,000 were offered for information leading to arrests.
Ramos said 70 members of an elite military Special Forces unit had been sent to search for the prison along with federal police, as reported by The Guardian. The US customs and border protection agency said it was aware of the prison break and officials were in communication with Mexican law enforcement authorities, according to an emailed statement.
Ramos said in a press conference that police were investigating a shootout 160 miles south of Piedras Negras after the escape to determine if any of the four people killed were fugitives.
He said 86 of the escaped inmates were serving sentences or awaiting trial for federal crimes, such as drug trafficking, and the rest faced state charges.
Other Mexican states have said in the past that they are not prepared to handle highly dangerous federal prisoners.
It was one of the larger prison breaks to hit Mexico's troubled penitentiary system in recent years. In December 2010, 153 inmates escaped from a prison in the northern city of Nuevo Laredo. Authorities charged 41 guards with aiding inmates. Mexico's drug gangs frequently try to break their members out of prison.
Coahuila, where Monday's prison break took place, has seen a wave of violence tied to the brutal Zetas cartel's battles with the Sinaloa cartel, allies of the now-weakened Gulf cartel.
Authorities in Coahuila did not say which gang was believed to be behind the escape. Last week, Gulf cartel leader Jorge Eduardo Costilla Sanchez was arrested, leading experts to anticipate an increase in violence in parts of northern Mexico as the Zetas attempted to take over their turf. In Piedras Negras, family members had gathered outside the prison to hear news of their loved ones.
