Big border-crossing tunnel found linking Tijuana, San Diego

SAN DIEGO, Calif. - U.S. authorities earlier this week announced the discovery of an underground smuggling tunnel on Mexico’s border, running the length of a football field on U.S. soil to a warehouse in an industrial area.

The cross-border tunnel from Tijuana to the San Diego area was built in one of the most fortified stretches of the border, illustrating the limitations of former President Donald Trump’s border wall. While considered effective against small, crudely built tunnels called "gopher holes," walls are no match for more sophisticated passages that run deeper underground.

Authorities have found about 15 sophisticated tunnels on California’s border with Mexico since 2006, with hallmarks including lighting, ventilation, railway tracks and hydraulic lifts.

Many tunnels, including the one announced Monday, are in San Diego’s Otay Mesa industrial area, where clay-like soil is conducive to digging and warehouses provide cover.

The cross-border passages date back to the early 1990s and have been used primarily to smuggle multi-ton loads of marijuana. The U.S. Drug Enforcement Administration said in 2020 that they are generally found in California and Arizona and associated with Mexico’s Sinaloa cartel.

By federal law, U.S. authorities must fill the U.S. side of tunnels with concrete after they are discovered.