The Mexican government’s shuttering of a special criminal investigative unit that worked with US anti-drug agents has added new cracks in a security relationship that once formed the foundation of efforts to combat organized crime in both countries.

Mexican president Andrés Manuel López Obrador said at an April 21 news conference that his government had dismantled “more than a year ago” a Sensitive Investigative Unit (SIU) that worked with the US Drug Enforcement Administration (DEA). The statement came a few days after Reuters published a report on the unit’s closure in April 2021. Before that, Mexican authorities had not yet made the decision public.

The shutdown came months after the release of Salvador Cienfuegos, Mexico’s former defense minister, whose US arrest on drug trafficking and corruption charges sparked outrage from the Mexican government.

SEE ALSO: Mexico Clears Ex-Defense Minister, Accuses US of ‘Fabricating’ Drug Charges

However, it was a US plea deal in the case of disgraced former SIU commander Iván Reyes Arzate, who served from 2008 to 2016, that was the “final straw” for the Mexican government, pushing it to close the unit, Proceso reported. Last year, Reyes Arzate pleaded guilty to receiving thousands of dollars in bribes from a drug trafficking organization in exchange for filtering confidential intelligence to a criminal federation known as El Seguimiento 39. In exchange for his testimony, he was sentenced to just ten years in prison.

In the past, the DEA has described the SIUs as one of its “most successful programs” for dismantling international drug trafficking organizations. Since 1997, the SIUs in Mexico, which first operated under the Federal Police and then the National Guard, have collaborated with US authorities to capture some of the country’s most notorious kingpins, such as Joaquín Guzmán Loera, alias “El Chapo.”

The Mexican president justified the unit’s closure on the grounds that it had been infiltrated by organized crime and assured that bilateral cooperation continues, but “under other terms.”

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The shutdown of the SIU in Mexico comes at a time when the two country’s security efforts have grown increasingly strained.

The US arrest of former Defense Minister Cienfuegos at the end of 2020 first triggered acrimony on the part of the government of Lopéz Obrador, given that the administration had no knowledge of the investigation. Several months later, President López Obrador exonerated Cienfuegos and accused the DEA of “fabricating” the charges against him.

At that time, Mexican lawmakers also amended the national security law to restrict operations by foreign agents in the country – a move that affected US investigators. Days before the reform was approved, the US Attorney General expressed concern, saying that these changes would hinder security and justice cooperation between the two countries.

SEE ALSO: InDepth Coverage of the US/Mexico Border

For Mike Vigil, the former chief of the DEA’s international operations, the closure of the SIU is just the latest example of the two country’s diminishing trust in security operations.

The SIU was the main channel through which authorities in both countries exchanged confidential information on cross-border drug trafficking. Although there is still a unit of this type that collaborates with the Attorney General’s Office, it has less operational capacity.

By closing this information pipeline, Vigil said future exchanges of US intelligence will be made more difficult because there will be less certainty on the part of US agencies about who is receiving such information.

“Unfortunately, by dismantling the SIU, it puts the DEA and other law enforcement agencies in a quandary because they are not going to be able to pass ultra-sensitive information and be assured that it’s not going to be compromised,” Vigil told InSight Crime.

The units, however, have also been accused of stoking violence and of engaging in corruption throughout the region. An investigation by ProPublica discovered that an SIU leak in 2011 had triggered a massacre in northern Mexico in which about 60 people were killed. And in Colombia, former police captain Juan Pablo Mosquera, who ran an SIU in the city of Cali, was also accused of selling evidence and information to criminal actors.

Maureen Meyer, the Vice President of Programs for the Washington Office on Latin America (WOLA), noted that the corruption that existed within the SIU was already making the exchange of information difficult. The lack of oversight and accountability for this unit was an immediate concern for both governments, given that the filtering of information had driven violent episodes.

“A new relationship on security cooperation has had to be developed with clear limits on where and how US agencies can be involved in law enforcement affairs in Mexico,” Meyer said.

While Meyer agreed that trust between the two governments has been strained, she said that there are signs that the two governments continue to engage, such as the signing of the Bicentennial Agreement, a renewed bilateral effort to fight against transnational organized crime and other security issues.

“This is a clear sign of both governments’ commitment to cooperation on security issues,” Meyer said.