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Drug tunnel

In this undated photo provided by the United States Drug Enforcement Administration, shows a 240-yard, a complete and fully operational tunnel that ran from a small business in Arizona to an ice plant on the Mexico side of the border, Thursday, July 12, 2012, in San Luis, Ariz.(AP Photo/Drug Enforcement Administration)

Mexico's smuggling tunnels

A look at various smuggling tunnels across the U.S.-Mexico border.