Mexico government has offered a $3.8m reward for the capture of fugitive drug lord Joaquin "El Chapo" Guzman and sacked top prison officials amid suspicions that guards helped him escape.
Guzman escaped from his cell late on Saturday even though he was wearing a monitoring bracelet and surveillance cameras were trained on the room 24 hours a day, Interior Minister Miguel Angel Osorio Chong said on Tuesday.
Osorio Chong said Guzman "must have counted on the complicity of prison personnel... which if confirmed would constitute an act of treason".
Guzman, the head of notorious Sinaloa drug cartel, had been behind bars for just 17 months when he escaped for the second time since 2001, dealing a humiliating setback to President Enrique Pena Nieto's administration.
This time Guzman managed to flee a maximum-security prison some 90km west of Mexico City through a 1.5-km tunnel found under his cell's shower.
"What happened two days ago is a terrible event that has angered Mexican society," Osorio Chong said.
While cameras were constantly trained on the cell, Osorio Chong said there were "two blind spots," while the bracelet only worked inside the prison.
Osorio Chong said he decided to fire the Altiplano prison's director as well as the head of the nation's penitentiary system and general coordinator "to facilitate" the investigation.
Attorney General Arely Gomez said 34 prison officials and 17 inmates were interrogated by prosecutors. No charges have been announced so far.
A federal official said prison employees of various rank, including the warden, spent the night at the anti-organised crime unit of the attorney general's office.
The guards in charge of the capo's cell and those who monitored the surveillance cameras that look into the room were among those interrogated, the official said.
Two of Guzman's lawyers were questioned and anybody else who visited him during his incarceration is being sought.
The owner of the property where Guzman's tunnel ended also faced questioning.
The government has launched a massive manhunt for Guzman, who amassed a huge wealth as the head of the country's most powerful drug gang, with tentacles reaching around the globe.