The tunnels have been used for a variety of contraband, but they are most suited to marijuana smuggling. Bulky and odorous, marijuana shipments are more troublesome to take through customs on the ground.
Packs of marijuana are stored in a tunnel in Tijuana, November 3, 2010. US border police found a sophisticated drug smugglers' tunnel the length of six football fields linking Southern California with Mexico and arrested two people, authorities said. Agents recovered more than 25 tonnes of marijuana in seizures related to the investigation in both California and Mexico and arrested a US citizen and his Mexican wife.