It took just minutes. Not a shot was fired. And by Sunday, authorities were sure it was an inside job.
Suspected drug traffickers swept into the prison in Zacatecas state Saturday and freed 53 inmates. Many of the escapees were cartel gunmen.
State Gov. Amalia Garcia said the prison warden and two top guards had been arrested. An additional 40 guards were being questioned.
"It is clear to us that this was perfectly planned" and that guards were bought off, Garcia said.
Officials reached that conclusion after reviewing tapes from security cameras. The footage shows the ease with which a convoy of 17 vehicles, backed by a helicopter, approached Cieneguillas prison. About 30 men, some in police uniforms, entered, rounded up the prisoners, loaded them into the cars and sped away.
The use of a helicopter was especially worrying to investigators, because they are not common in the Zacatecas area.
Army and federal security forces fanned out through four states in search of the escapees. Most of them were associated with the notorious Gulf cartel, one of Mexico's most powerful and violent drug gangs, and their paramilitary force, gunmen called the Zetas.
Once a relatively peaceful region, the central mountainous state of Zacatecas has become a venue for kidnappings, extortion and other violent crimes that have eroded the local economy and chipped away at government authority. In recent years, the Gulf cartel moved in and began to challenge the Pacific coast-based Sinaloa drug dealers who traditionally operated in Zacatecas and used it as a corridor for smuggling routes.
It was the third prison break in Zacatecas in recent years. It took place before dawn Saturday. Meanwhile, in Veracruz state, in a similar operation, commandos freed six inmates.
Among those who escaped in Zacatecas were several convicted drug traffickers, killers and kidnappers. They were housed in the maximum security division of the prison. Late Sunday, officials ranked 11 of the 53 escapees as "highly dangerous" and circulated their photographs to the public.
Hundreds of traffickers have been arrested by government forces over the years, but most of the top leaders remain at large or have been extradited to the U.S. And when they are caught, they often bribe their way to freedom.
One of Mexico's most powerful drug lords, Joaquin "Shorty" Guzman famously escaped from a high-security prison in 2001 by hiding in a laundry truck.