US-Mexico border tunnel nets 40 tons of pot

In this undated photo provided by the United States Drug Enforcement Administration, shows the tunnel shaft entrance on the U.S. side of a 240-yard, complete and fully operational drug smuggling 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)Three drug smuggling tunnels equipped with lighting and ventilation — including one with a railcar system — have been discovered along the U.S.-Mexico border in less than a week, the latest signs that cartels are building sophisticated passages to escape heightened detection above ground.