It took the prison guards 18 minutes to go into Mexican drug lord Joaquin "El Chapo" Guzman's cell after they noticed that he vanished from his cell, authorities said on Thursday.
Interior minister Miguel Angel Osorio Chong said guards who monitored the surveillance cameras inside Guzman's cell "immediately" sounded the alarm when they noticed that "he was no longer there" late on Saturday.
"The arrival of guards (in the cell) took place 18 minutes later," Osorio Chong said after he and other law enforcement officials met with Congress's security committee to discuss the escape .
Prosecutors are investigating whether the prison's protocols were properly followed, he said, adding that the Altiplano prison some 90km west of Mexico City was placed on lockdown after the escape and that authorities went through the tunnel.
Watch: Joaquin "El Chapo" Guzman's last moments in prison
It was the first time that officials said how long it took for guards to respond after Guzman disappeared into a hole on the floor of his shower.
Closed-circuit camera footage released by the government this week showed that Guzman paced in his cell before bending down behind a short partition wall in the shower.
The Sinaloa cartel chief then rode on a motorcycle with two carts rigged on a rail system inside a 1.5km tunnel built for his second escape in 14 years.
The 18 minutes it took for guards to enter his cell gave him a big head start.
Authorities have held 22 prison officials for questioning since Sunday but have yet to file any charges amid growing suspicions over inside help.
Guzman escaped only 17 months after Mexican marines captured him in February 2014 in the Sinaloa state resort of Mazatlan with the help of US law enforcement agencies.
Attorney General Arely Gomez told the lawmakers that Mexico formally received a US extradition request for Guzman on June 25, some two weeks before his escape, her office said in a statement.
Gomez instructed prosecutors to analyze the request after it was received, the statement said.
Mexican authorities have come under fire for failing to keep the nation's most powerful drug kingpin in prison, raising questions about why it never extradited him to the United States, where prisons are deemed more secure.
Gomez's predecessor, Jesus Murillo Karam, had said last year that Guzman would have to serve his time in Mexico before he would be extradited to the United States.
'Certain' to catch him
The escape has become a huge embarrassment to President Enrique Pena Nieto, who was flying to France for a state visit the night that Guzman escaped. He returns to Mexico on Friday.
The government has offered a $3.8 million reward for Guzman's capture, placing full-page newspaper ads and distributing 100,000 leaflets with three different pictures of the fugitive.
Thousands of police are looking for him in a massive manhunt that includes raids in hotels, hospitals and funeral homes.
"We are all over the country, watching roads, villages, borders, airports," Federal Police chief Enrique Galindo told reporters. "We have one mission: Bring Joaquin Guzman to prison."
"We have arrested him before, we have put him behind bars before," Galindo said.
"We are certain that we will get him."