The Sinaloa cartel, under Guzmán's direction, "basically was the impetus for building tunnels across into the United States," Vigil said. "They started to then put in ventilation. They started to put in lighting, railroad carts to facilitate the movement of drugs and actually illegal aliens through those tunnels, and they became much longer, and they started to riddle the Mexican border with a massive amount of tunnels."
John Morton, left, director of the US Immigration and Customs Enforcement (ICE), stands inside a warehouse near the Mexican border where a long tunnel was found in Otay Mesa, California, November 3, 2010. US border police have found a sophisticated smuggler's tunnel the length of six football fields linking Southern California with Mexico and believed to have been used by drug traffickers, authorities said. Agents also recovered more than 20 tons of marijuana during overnight searches of the tunnel, the border patrol said in a news release.