Zambada said in a letter that he was kidnapped in Mexico and brought to the U.S. by Guzmán López, son of imprisoned Sinaloa co-founder Joaquín "El Chapo" Guzmán.

Zambada is the eldest son of Ismael “El Mayo” Zambada García, a longtime leader of the so-called Sinaloa Cartel, a federation of drug lords that has long controlled smuggling routes in ...