There had been nervousness about the impending return of Cárdenas Guillén, who once led the feared Gulf cartel in northeastern Mexico before he was arrested and extradited to the United States in 2007.
The U.S. Homeland Security Department confirmed in its social media accounts Monday that Cárdenas Guillén had been returned after serving 14 years in U.S. custody, most of his 25-year U.S. prison sentence. He is a Mexican citizen, so presumably he was deported.
A Mexican federal official who was not authorized to be quoted by name said Cárdenas Guillén had immediately been taken into custody in Mexico on drug, organized crime and money-laundering charges.
The official said Cárdenas Guillén was being held at the country's top maximum-security Altiplano prison just west of Mexico City.
Homeland Security Investigations posted photos of a paunchy, balding, bespectacled Cárdenas Guillén being escorted by two officers in helmets and flak vests, and the being walked over a border bridge.
The image contrasts with the drug lord's fearsome reputation for violence in Mexico.
The former head of the Gulf cartel was known for his brutality. He created the most bloodthirsty gang of hitmen Mexico has ever known, the Zetas, which routinely slaughtered migrants and innocent people.
The 57-year-old native of the border city of Matamoros, Mexico, moved tons of cocaine and made millions of dollars through the Gulf cartel, based in the border cities of Reynosa and Matamoros.