Bold prison break? Just another day in Mexico's drug war.

A convoy of cars carrying more than two dozen suspected drug cartel members disguised as Mexican police officers arrives at the Zacatécas state prison before dawn. Their helicopter hovers overhead. Minutes later, the men help more than 50 inmates – many of them suspected drug traffickers – flee the prison. A countrywide manhunt ensues.

No, this is not a script for a B movie. It's just another day in Mexico's high-stakes war on drug trafficking – Saturday, in fact.

The story grabbed headlines worldwide. But for Mexicans – who have now grown accustomed to fugitives on the lam and traffickers taunting the state with death threats and even banners hung in public spaces to recruit new members – it was business as usual.

"[Drug traffickers] are sticking their tongues out at us," says Erubiel Tirado, a security expert at the Iberoamerican University in Mexico City. "They don't care if we have military in the streets. They are capable of breaking into a hospital and executing [a rival]. There is no one who can stop them."

Many of those who fled from the Cieneguillas prison in Zacatecas over the weekend are believed to be members of the Gulf cartel, one of the major organizations fighting the Mexican state and their rivals to preserve corridors to the illegal drug market in the US.

A history of prison breaks

Prison breaks are nothing new in Mexico. In 2001, Mexico's most wanted drug lord, Joaquin "El Chapo" Guzman, escaped from a high-security prison – reportedly in the back of a laundry truck. And there have been at least three breaks in Zacatecas in recent years.

Such attempts began in the late 90s, says Mr. Tirado, with the emergence of the Zetas, who are the security enforcers for the Gulf Cartel. "This is know-how from the Zetas; it is their MO," he says.

The governor of Zacatecas called it an inside job. "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," said Zacatecas Gov. Amalia Garcia Medina at a new conference. Prison employees were detained for questioning.

A tough fight against corruption

It's another blow to President Felipe Calderon's pledge to root out the scourge of corruption that runs up and down government agencies. Former police chiefs and public security officials throughout the country have been arrested for receiving payment or protection from the cartels.

This weekend, authorities in southern Mexico nabbed half a dozen suspected Gulf cartel assassins – two of them women – who were allegedly commanded by top local police officers. Prosecutors announced this week that the top state security official and the police chief in a state capital in central Mexico were ordered held for 40 days on suspicion of aiding the Beltran Leyva cartel.

Those are only the latest in a long list of official ties to drug cartels revealed in the past couple years.

Alejandro Schtulmann, president of the consulting firm Emerging Markets Political Risk Analysis (EMPRA) in Mexico City, says he believes the Calderón administration won't pay politically for Saturday's jail break. "When a [high-profile] druglord escapes, that's really bad for the federal government, since the druglord is supposed to be in a high-security compound," he says. The break in Zacatecas, which included no deaths and not even any gunfire, is more likely to have consequences for the state governor, he says.

Retooling prison security

Not unlike what Calderón has done, some states have put former military members in charge of public security and state prison systems. "What Chihuahua and other states have been doing is they have been militarizing the post to oversee the prisons in the state, as a means to bring new security elements that are less prone to corruption," says Mr. Schtulmann. "I think this [incident in Zacatecas] could have been avoided; my impression is that for such a thing to happen, the security was really bad."

Calderón has acknowledged vulnerabilities within the prison system, significantly stepping up extraditions to the US of suspected drug traffickers compared to the previous administration. There have been nearly 200 extraditions to the US since he took office, underlining not just cooperation with the US but an inability of the state to make sure that those arrested stay behind bars.

• Wire services were used in this report.