NUEVO LAREDO - Some 5,000 Mexican troops and police officers mounted a manhunt along the US border Tuesday for 132 inmates who escaped in broad daylight through a tunnel dug under their prison. Backed by a helicopter, soldiers and officers fanned out across the region bordering Texas, causing traffic jams as they inspected trucks and cars, one day after the massive prison break in the northern state of Coahuila.

“There are some 5,000 soldiers and police officers in the operation and authorities in four Mexican states and Texas have been alerted,” Coahuila public security chief Jorge Luis Moran told Milenio radio. The prisoners escaped one-by-one Monday through a seven-meter-long (22-foot-long) tunnel that was started in the carpentry workshop and surfaced at the prison’s northern watchtower in the border city of Piedras Negras. After emerging from the tunnel, the inmates cut through a perimeter fence and slipped away through a vacant lot, Coahuila state attorney general Homero Ramos Gloria said in a statement. Ramos was quoted as saying in El Universal newspaper that the breakout was believed to have occurred shortly after 2:00 pm local time, but it was at least another hour before guards discovered the inmates were gone. The prison’s director, security chief and shift guard have been detained and all of the penitentiary’s guards will be summoned for questioning over possible complicity in the escape, Ramos told broadcaster Televisa. The guards must explain “why nobody found out that this tunnel was being built,” he added.