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A Mexican soldier stands guard next to packages of marijuana found at a warehouse in Tijuana, Mexico, on Wednesday, Nov. 16, 2011. Approximately 17 tons of marijuana were discovered in a cross-border tunnel that appears to be one of the most significant drug smuggling passages found between the U.S. and Mexico. Photographer: David Maung/Bloomberg via Getty Images

A Mexican soldier stands guard next to packages of marijuana found at a warehouse in Tijuana, Mexico, on Wednesday, Nov. 16, 2011. Approximately 17 tons of marijuana were discovered in a cross-border tunnel that appears to be one of the most significant drug smuggling passages found between the U.S. and Mexico. Photographer: David Maung/Bloomberg via Getty Images