In this December 2012 file photo, Jack Riley, head of the Drug Enforcement Administration in Chicago, points out local Mexican drug cartel problem areas on a map in the new interagency Strike Force office in Chicago. Looking on is DEA agent Vince Balbo. The ruthless syndicates have long been the nation's No. 1 supplier of illegal drugs, but in the past, their operatives rarely ventured beyond the border. A wide-ranging Associated Press review of federal court cases and government drug-enforcement data, plus interviews with many top law enforcement officials, indicate the groups have begun deploying agents from their inner circles to the U.S.