When a convoy of heavily armed federal police arrived at the maximum-security Cieneguillas jail, nothing appeared out of the ordinary.

Five minutes later, however, 53 inmates — including more than two dozen members of one of Mexico’s biggest drugs gangs — had been freed in an audacious jailbreak. The police uniforms had been fake and the gunmen were in fact members of the criminal Gulf cartel.

As a manhunt got under way last night it appeared that Mexico’s drugs gangs had scored another embarrassing victory over President Calderon’s efforts to crush the menace of the increasingly powerful cartels.

About 20 gunmen arrived at the prison before dawn yesterday in 10 vehicles and freed 53 prisoners, including at least 27 with ties to the Gulf gang.

Amalia Garcia Medina, governor of the state of Zacatecas, in central Mexico, said that the jailbreak may have been revenge for the recent arrests of gang members and the seizure of guns and drugs by the state police.

“This will not go unpunished,” she said. “The investigations will be conducted with the full weight of the law to their last consequences.”

First reports suggested that the prison guards had been overcome in a carefully orchestrated operation, but later evidence emerged to suggest that some of the guards had been in on the job, according to footage from security cameras.

Ms Garcia said: “It’s clear to us that it was a perfectly planned operation with inside help because it lasted just five minutes and not one shot was fired.”

The prison’s director, 40 guards and two police commanders who were on duty at the time were being questioned.

Corruption among police and other officials has been a key obstacle in Mexico’s US-backed war against the ruthless drugs gangs.

Mr Calderon has acknowledged that corruption permeates all levels of the Mexican police and has sent more than 45,000 soldiers to fight the cartels.

However, allegations of brutality by the army have surfaced during the offensive, and drug-related violence has become increasingly savage as rival gangs fight each other for territory and stage bold attacks against police.

Beheadings and assassinations of police officers have been increasing. Last month, about 20 gunmen fought a running battle with prison officers as they ambushed a prisoner transfer convoy in western Mexico. Eight prison officers died in a failed attempt to free Jeronimo Gamez,a high-ranking cartel member. The same month, 400 police arrested 44 members of the same drugs gang as they celebrated a family baptism.

In January, police arrested Santiago Meza Lopez – known as The Stewmaker – who admitted disposing of the bodies of about 300 enemies of one cartel leader.

Drug-related violence killed more than 6,000 people last year alone. Mexico has arrested at least 327 cartel members since Mr Calderon took office, but the top leaders remain at large.

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