Chicago and its suburbs are among the places Mexican cartels are dispatching trusted operatives.
An Associated Press review of federal records suggests cartels in recent years have increasingly begun sending agents directly from Mexico deep into the American heartland.
Records indicate the La Familia cartel sent Jose Gonzalez-Zavala to Joliet, where he ran a drug network from a suburban home starting in 2008.
Atlanta-area prosecutor Danny Porter says cartels rely on fear to ensure such agents stay in line.
Porter says detained cartel members laugh when he asks if they'll cooperate for lesser sentences. They say cartel bosses will "boil" their families "in acid" if they dare reveal cartel secrets.
Gonzalez-Zavala told his sentencing judge in 2011 such fear kept him from cooperating. He received a 40-year prison term.