A violent prison break in which 30 inmates escaped and 17 people — mostly guards — were killed has revealed a shocking level of self-rule by prisoners inside a prison in the northern Mexico border city of Ciudad Juárez.

Not only were criminals able to sneak guns, drugs and luxury goods into prison Number 3, they actually held the keys to some sections of the facility, which is located across the border from El Paso, Texas.

“It was evident that the inmates themselves were practically in charge of security, and that on some cell blocks, they had the keys to common areas, like classrooms or cafeterias,” said Néstor Manuel Armendáriz, president of the Human Rights Commission in the northern state of Chihuahua.

Searches after Sunday’s uprising and jailbreak turned up 10 “VIP” cells outfitted with televisions and other comforts. One even had a safe filled with cash. Authorities also found cocaine, methamphetamine, heroin, fentanyl and marijuana inside the prison, and they found 14 guns just outside.

But Armendáriz said supposed searches in 2021 didn’t find any of that.

Ten of the dead were prison guards who were attacked by gunmen who arrived early in armoured vehicles and fired on the entrance and inside dormitories. The seven other dead included two policemen and five suspected attackers.

The director of the prison was fired on Tuesday, and 191 inmates considered high-risk were transferred out of the overcrowded prison.

The inmates who escaped have been identified as members of the Mexicles gang; the Mexicles’ leader, who was serving a sentence for murder and other crimes, was among the fugitives. The Mexicles have been one of Juárez’s main gangs for decades, and for many years were known to work with the Sinaloa Cartel.

At the time of the jailbreak, prison Number 3 held 4,000 inmates, 23 per cent more than it was designed to hold. As is common in Mexican prisons, people awaiting trial — 90 per cent of inmates at the Ciudad Juárez facility — are mixed in with convicted criminals.

Despite the prison’s long history of problems, authorities prefer to look the other way, said Saskia Niño de Rivera, who leads the incarceration reform group Reinserta.

“Security is totally politicised because the prisons don’t win you political points,” said Niño de Rivera.

The problem is particularly sensitive in Ciudad Juárez, where local gangs work for drug cartels and any violence inside prisons can quickly spill out onto the streets of the city.

That happened in August, when a violent riot inside the same state prison spread to the streets of Juárez and left 11 people dead.

She said Sunday’s riot was “a clear example of what is occurring in a large number of Mexican prisons, which are completely forgotten by the authorities and which are completely out of control.”

In 2016, 49 inmates were killed in a riot at the notorious Topo Chico prison in the northern border state of Nuevo León. Investigators found the prison to be full of contraband and weapons. The state government finally closed it in 2019.

Mexico has a prison population of some 226,000 people, many held in overcrowded conditions in prisons without sufficient guards. The problem is fed by policies that allow, and in some cases require, suspects to be held for a wide variety of crimes for long periods before trial.