Mexican prosecutors investigating the escape of drug kingpin Joaquin "El Chapo" Guzman have formally placed 22 prison officials in custody over suspicions that the infamous fugitive had inside help.
While a massive manhunt for Guzman entered its third full day, the attorney general's office released 12 of 34 prison staff members who had been questioned since Sunday.
Interior Minister Miguel Angel Osorio Chong said on Monday that Guzman "must have" had help from prison officials in his brazen escape on Saturday.
The episode saw Guzman slip out of his cell through a 1.5km tunnel dug under his private shower in the Altiplano maximum-security prison, some 90km west of Mexico City.
"There are 22 people who arrived as witnesses and their legal situation has changed to detainees. This means [prosecutors] presume that there was some sort of participation" in the escape, said an official in the attorney general's office.
Authorities now have 96 hours to either charge or release them.
The official refused to say whether the prison's director, who was fired on Monday, was among those released or kept in custody.
Prosecutors have also questioned two of Guzman's lawyers and the owner of the property where the drug lord's tunnel ended.
The escape marks the second time since 2001 that Guzman managed to flee a maximum-security prison, dealing a humiliating setback to President Enrique Pena Nieto, just 17 months after his much-celebrated capture.
Mexico has released a video showing the moment that Guzman goes into his prison cell's shower before disappearing.
The surveillance camera footage shows Guzman pacing back and forth several times in the cell before bending down behind a short dividing wall in the shower space, but the hole through which he escaped is not visible.
National Security Commissioner Monte Alejandro Rubido said Guzman's behaviour before he vanished late on Saturday was normal for an inmate in a maximum-security prison.
"It's a natural behaviour for prisoners in a confined space for a prolonged time," Rubido told reporters.
The Government also showed a video of the 1.5km escape tunnel, which had a rail system for a motorcycle with a metal cart for it to ride on.