RENEE MONTAGNE, HOST:

And in Mexico, more details are emerging about how that country's most notorious drug trafficker escaped from a maximum security prison again. To build the series of tunnels that Joaquin El Chapo Guzman used to slip out of his cell, he and his accomplices had to have had the help of officials. Not only that, but they would have needed blueprints for the prison and about a year to build the tunnel. That's what a leading government minister and Mexican engineering experts are saying as they try to work out how he did it. NPR's Carrie Kahn has more from Mexico City.

CARRIE KAHN, BYLINE: Interior Secretary Miguel Angel Osorio Chong vowed to recapture the kingpin and announced a $3.8 million reward for information leading to his arrest.

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MIGUEL ANGEL OSORIO CHONG: (Speaking Spanish).

KAHN: "There will be no rest for this delinquent," Osorio Chong told reporters. "This criminal has committed multiple murders," he said, "and has sold millions of doses of drugs that have harmed our children." The warden and two top prison officials have been let go. More than 45 others have been questioned in the investigation, including Guzman's personal lawyers and prisoners housed near him. Thirty-four prison employees remain in custody.

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OSORIO CHONG: (Speaking Spanish).

KAHN: "There will be no place for impunity," says Osorio Chong. "Any public officials found to have participated in this crime will be punished." Osorio Chong says he has no plans to resign his post. Guzman's break has proven to be one of the biggest embarrassments of Enrique Pena Nieto's administration and is expected to further hurt the president's plummeting approval ratings, now at around 40 percent. Pena Nieto remains on a state visit to France. Pictures of the president touring Napoleon's tomb and hosting a gastronomic festival aren't helping him back home. Top that with the repeated play in the Mexican media of his statements that it would be deplorable if Guzman escaped and proclamations by his then-attorney general that the capo would never be extradited to the U.S.

ALEJANDRO HOPE: I think it was an egregious mistake not to extradite him.

KAHN: Alejandro Hope, a security editor at El Daily Blog, says it's shocking the hubris top Mexican officials exhibited about their ability to prosecute and securely imprison Guzman given his first escape in 2001. Hope says Mexican nationalistic pride got in the way of making smart decisions regarding Guzman's incarceration. He says there was also a fear in Mexican intelligence circles that if U.S. agents got Guzman, they would flip the kingpin.

HOPE: They would turn him into an informant and whatever information, whatever intelligence, they could gather from him would never flow back to Mexico.

KAHN: But while distrust seemed to play a role in Mexico not extraditing Guzman to the U.S., it remains unclear whether American officials formally made the request. When asked, a spokesman for the U.S. Department of Justice would only say that it has been a subject of ongoing discussions between the two countries. Notre Dame law professor and former FBI agent Jimmy Gurule says Guzman's brazen escape has only further damaged binational cooperation.

JIMMY GURULE: And until that confidence is regained, I think this sharing of sensitive and classified information by the U.S. and Mexican law enforcement officials is going to continue to be a serious problem.

KAHN: Not helping the situation are revelations that as early as last year, the DEA alerted Mexico that Guzman and his associates were hatching two escape attempts. The Associated Press says it obtained documents from the anti-drug agency revealing the plots. Mexico's interior secretary denied ever receiving that information. Carrie Kahn, NPR News, Mexico City. Transcript provided by NPR, Copyright NPR.