Drug kingpin Joaquín “El Chapo” Guzmán is on the run once again after escaping from a maximum-security prison outside Mexico City. Guzmán used a method that has helped his cartel make billions: highly sophisticated tunnels. (Jason Aldag/The Washington Post)

To build a tunnel about a mile long and 30 feet below Mexico’s highest-security prison, the rescuers of drug lord Joaquín “El Chapo” Guzmán would have needed to haul away several hundred truckloads of earth and use excavating power tools that would have been difficult not to hear.

To guide their burrowing exactly under the shower stall in Hall 2, Cell 20, of the special-treatment wing for the country’s most dangerous criminals, the tunnelers would have needed detailed knowledge of the prison’s layout, information considered a state secret.

And Mexico’s prison administrators had to have been aware of the risk of an escape attempt — Guzmán had made his way out of a high-security prison once before.

During the year and a half that Guzmán was incarcerated in Altiplano Prison, the U.S. Drug Enforcement Administration told Mexican officials that his relatives and associates were plotting various efforts to try to spring him from jail, according to U.S. law enforcement officials who spoke on the condition of anonymity.

Mexican officials in the attorney general’s office and on the National Security Commission said Monday that they had no information about whether they had received American warnings in the past.

But questions now center on whether Mexico’s most audacious prison break was simply a feat of engineering genius and clandestine planning — or whether other factors were at play.

Mexico’s interior minister, Miguel Angel Osorio Chong, who toured the prison Monday, told reporters later in the evening that Guzmán could not have escaped without the complicity of prison officials, calling it an act of “disloyalty and treason” to Mexicans and the security forces who “risked their lives to capture him.” He said Guzmán had been wearing a tracking bracelet and his cell had a 24-hour video surveillance system that was monitored by people working in three shifts. The Mexican government offered a reward of 60 million pesos ($3.8 million) for information leading to his rearrest.

The potential collusion of the prison staff — and the people who came to visit Guzmán during his time behind bars — became a priority for the investigation the day after authorities learned of the cartel leader’s disappearance and as they began to reckon with the fallout of his escape.

“Today, the Mexican state is the laughingstock of the world,” said José Guillermo Anaya Llamas, a congressman from the opposition National Action Party and the head of the legislature’s public security commission. “There has to be an exhaustive review of the Mexican penal system.”

Experts on the prison system said they assumed that at least some prison employees must have been aware of the impending escape.

“The supervision should have been very strict, given the profile and relevance for the Mexican government of this drug lord,” said Eduardo Guerrero Gutiérrez, a security consultant and former intelligence official. “They should do a complete cleaning of this prison staff. There was massive collusion.”

In addition to his lawyers, Guzmán was reportedly visited by a congresswoman from his home state of Sinaloa, Guadalupe Sánchez. She denied that she had any relationship with Guzmán or did anything to help him plot his escape.

On Monday, the manhunt spread across several states, and soldiers and police officers searched cars and manned checkpoints. Those closer to the scene of the crime were interrogated about whether they had any knowledge of Guzmán’s plot to escape — mirroring in some ways the internal probes after two inmates slipped away from a maximum-security prison in northern New York last month to begin three weeks on the run.

The attorney general’s office said more than 30 members of the prison staff have been questioned, including the director, Valentín Cárdenas Lerma.

U.S. law enforcement officials have offered to help the Mexican government in that effort, but so far the Mexicans have not indicated whether they will accept. Attorney General Loretta E. Lynch spoke with her Mexican counterpart by phone about the case. Guzmán’s escape has infuriated American law enforcement officials who worked for years to capture him and pushed for his extradition to the United States.

White House press secretary Josh Earnest said that Guzmán had a “long rap sheet” and that his Sinaloa cartel has “committed a significant number of crimes and does pose a threat to public safety, not just in Mexico but in the United States as well.”

Earnest said that the White House is “very concerned about making sure that Mr. Guzmán is brought to justice.”

In Mexico, few people were optimistic about the government’s chances of finding him anytime soon. From political talk shows to the farming communities scattered around the prison, Mexicans considered it anything but surprising that a rich and powerful criminal might have been able to buy his way to freedom.

In Guzmán’s 2001 vanishing act from the Puente Grande prison in the western state of Jalisco, corrupt guards played a key role, allegedly hiding him in a laundry cart.

His second escape has come to be seen as an egregious example of a fatal weakness in Mexico’s fight to make the country safer: that payoffs and kickbacks are so common, government officials cannot be trusted to work against organized crime.

It “reveals the weakness of the institutions of the Mexican state, the criminal infiltration at the highest levels,” said Denise Dresser, a columnist and political science professor.

Not everyone agreed. Given the regular construction just outside the prison — the government has been installing water pipes in a large trench running along the perimeter fence — and renovations inside, some people said the tunnel construction could have gone unnoticed.

“They’re always fixing things in the jail,” said a lawyer who has clients in Altiplano and regularly visits. “They’re always putting up cables, painting, putting up tiles. It’s very loud in there.”

Gabriela Martinez contributed to this report. Sari Horwitz contributed from Washington.