MEXICO CITY - U.S. federal prosecutors charged Ismael "El Mayo" Zambada, the co-founder of Mexico's notorious Sinaloa drug cartel, with conspiracy to manufacture and distribute fentanyl, prosecutors in New York said on Thursday.

Zambada founded the Sinaloa Cartel along with now-jailed drug lord Joaquin "El Chapo" Guzman, and U.S. prosecutors allege he continues to lead the organization from hiding.

Thursday's fentanyl-related charges add to a litany of indictments for crimes relating to drug trafficking and organized crime.

"Fentanyl is the deadliest drug threat Americans have ever faced, and the Sinaloa Cartel continues to be the largest trafficker of fentanyl into the United States," DEA Administrator Anne Milgram said in a statement released by the U.S. Department of Justice.

Fentanyl is the leading cause of death for Americans between the ages of 18 and 45, Milgram said. REUTERS