Mexican President Andres Manuel Lopez Obrador
President of Mexico Andres Manuel Lopez Obrador speaks during the Ayotzinapa case report at Palacio Nacional on September 26, 2020 in Mexico City, Mexico. Hector Vivas/Getty Images

Mexican President Andrés Manuel López Obrador, also known as AMLO, accused the U.S. Drug Enforcement Administration (DEA) on Friday of fabricating drug charges against his country's former defense secretary Gen. Salvador Cienfuegos.

The Associated Press reported that AMLO's government also published what he said was the entire case file provided by DEA authorities when Salvador Cienfuegos was sent back to Mexico.

"Why did they do this investigation this way? Without substance, without evidence?" López Obrador said in a news conference, referring to the DEA case against Cienfuegos. López Obrador also said there was a lack of "professionalism" in the U.S. investigations.

On Friday, López Obrador backed the decision of the country's attorney general to dismiss any charges against Salvador Cienfuegos related to drug crimes, reported Reuters.

However, the case underscored the fragile diplomatic relations between the U.S. and Mexico, noted The Washington Post.

Salvador Cienfuegos Arrested in Los Angeles in October

It can be recalled that Salvador Cienfuegos was arrested at Los Angeles International Airport in October for charges related to working with the H-2 drug cartel that would ship thousands of kilos of drugs to the U.S.

Following fury from the Mexican government, he was sent back to Mexico for officials of his own country to look into his case. At the time, Mexico's government vowed to look into the matter thoroughly.

However, over a month later, the Attorney General's Office found no grounds to charge Salvador Cienfuegos and said the former defense chief had no connections with the criminal organization members. The Attorney General didn't find proof of any untoward increases in Cienfuegos' wealth as well.

"It's a decision the attorney general's office makes, but one that the government I represent supports," said López Obrador.

Cienfuegos' charges were all dropped, and he was never placed under arrest after crossing to Mexico. For Mexico, the failure to notify them prior to the arrest marked a "before and after" in bilateral ties.

In December, new rules governing the operations in the country of foreign agents, including the DEA, was created. Salvador Cienfuegos served as defense minister in Mexico from 2012 to 2018.

A spokesperson for the U.S. Department of Justice, Nicole Navas Oxman, said they are reserving the right to restart prosecuting him if the Mexican government chooses not to do so.

Salvador Cienfuegos is Highest Ranking Mexican Official on Drug Charges in U.S.

Salvador Cienfuegos is the most senior Mexican official to be arrested in the U.S. for drug-related crimes. His arrest was a point of outrage for the country's military, a pillar in López Obrador's government.

Documents released in connection to the case included purported texts between two drug gang figures who talked about having a meeting at the Defense Department with someone called "The Godfather" or "Salvador Sinfuego Sepeda."

The two drug figures, known to be Daniel Silva-Garate, and Juan Francisco Patrón Sánchez, were both later killed.

They described being picked up by men in military-cut hair who told them about going to the Defense Department in Mexico City.

"You can sleep peacefully, no operation will touch you," the said "Godfather" told them, according to Silva-Garate's messages.

Meanwhile, López Obrador insisted that his government will not be covering up for anyone.