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FILE - Accused Mexican drug kingpin Osiel Cardenas Guillen leaves the federal courthouse after pleading not guilty to charges connected to running a cartel, in Houston, Feb. 9, 2007. (AP Photo/Pat Sullivan, File)

FILE - Accused Mexican drug kingpin Osiel Cardenas Guillen leaves the federal courthouse after pleading not guilty to charges connected to running a cartel, in Houston, Feb. 9, 2007. (AP Photo/Pat Sullivan, File)

FILE - A soldier enters a bullet-riddled home covered by the initials of the Gulf Cartel (CDG) and Zetas (Z) in Ciudad Victoria, Tamaulipas state, Mexico, Sept. 6, 2014. (AP Photo/Eduardo Verdugo, File)

FILE - A soldier enters a bullet-riddled home covered by the initials of the Gulf Cartel (CDG) and Zetas (Z) in Ciudad Victoria, Tamaulipas state, Mexico, Sept. 6, 2014. (AP Photo/Eduardo Verdugo, File)