In this June 20, 2011, photo released by Mexico's Attorney General's office, police investigators look at drums of precursor chemicals for methamphetamine that were seized in Queretaro,

 

              In this June 20, 2011, photo released by Mexico
In this June 20, 2011, photo released by Mexico's Attorney General's office, police investigators look at drums of precursor chemicals for methamphetamine that were seized in Queretaro, Mexico. Over the last several years, the cartels have quietly swooped in to fill a void in the American drug market created by years of crackdowns that began more than a decade ago.(AP Photo/Attorney General's office, File)