The Mexican drug lord Ismael "El Mayo" Zambada and one of the sons of the cartel boss "El Chapo" have been arrested by authorities in Texas, according to the US Department of Justice.
The two cartel leaders were arrested in the border town of El Paso on Thursday.
They are accused of having controlled the cartel and its production and smuggling of fentanyl, a synthetic opioid that today accounts for around 70 percent of the US's fatal overdoses.
Zambada is said to have controlled the drug cartel's smuggling operations. He is a co-founder of the Sinaloa cartel, but has long kept a relatively lower profile than his notorious partner Joaquin "El Chapo" Guzmán.
The other arrested person is one of "El Chapo's" sons, Joaquín Guzmán López.
"The Department of Justice has taken into custody two alleged leaders of the Sinaloa cartel, one of the most violent and powerful drug trafficking organizations in the world," says US Attorney General Merrick Garland in a statement.
"El Chapo" is serving a life sentence in a high-security prison in Colorado, USA.
Another of the drug boss's sons, Ovidio Guzmán, has been detained in the US since he was extradited from Mexico. In connection with his arrest in January last year, 29 people were killed, including ten Mexican soldiers.
