Video footage has revealed that banging was audible in Mexican drug lord Joaquín Guzmán’s cell when accomplices tunneled inside to spring him in July

Loud hammering was audible in Mexican drug lord Joaquín “El Chapo” Guzmán’s prison cell when accomplices tunneled inside to spring him in July, but guards failed to act, according to recordings released by broadcaster Televisa.

Grainy video footage broadcast by Televisa revealed Guzmán turned up the volume on a televisual device by his bed to drown out the noise as his helpers hammered a hole through the floor under the shower, the only blind spot in the cell.

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The government, which was severely embarrassed by the escape, had previously shown some of the same CCTV footage of the minutes before Guzmán disappeared down the hole and escaped the maximum-security prison through a mile-long tunnel.

However, unlike Televisa, the government did not supply the accompanying audio of loud banging sounds that could be heard beneath the din of the Saturday night TV show playing in Guzmán’s cell as it was breached.

Media reports had previously said the noise of the jailbreak could be heard, but no audio had been broadcast until now. It was not clear why the government had not done so.

A spokesman for federal prosecutors could not immediately confirm whether the new audio was genuine.

Televisa also showed concurrent footage of what it said was the control center meant to be monitoring the prisoners in the Altiplano penitentiary not far from Mexico City.

Several people were shown watching their screens but apparently failing to notice or ignoring what was happening in Guzmán’s cell. However, it was not possible to see what was showing on the screens of the staff in the control room.

The government has so far arrested 34 people over the jailbreak, including a man suspected of being a pilot who flew Guzmán away from the site after his escape.

The interior ministry said shortly after Guzmán’s jailbreak that it could not have been possible without the collusion of guards and other officials, but questions remain about the full extent of cooperation the kingpin received.

The CCTV footage on Televisa showed that guards took more than 20 minutes to check his cell after he broke out, and waited a few more before entering and checking the escape hole.

Guzmán, boss of the powerful Sinaloa Cartel, was locked up after his capture by security forces in northwestern Mexico in February 2014. The jailbreak was his second, as he had previously escaped from prison in 2001.