A second San Diego drug tunnel has been detected and closed down by the local authorities. The operation, which took place on Thursday 25 November, resulted in a total of eight suspects being detained in Mexico and the USA, as well as the seizure of over 20t of marijuana, said the US Drug Enforcement Administration (DEA).

The tunnel stretches for almost half a mile (approx. 0.8km) from the Otay Mesa industrial complex in southern San Diego to Tijuana, Mexico. The tunnel has an estimated maximum overburden of 90 feet (27m). The walls were fitted with wooden and cinderblock supports. The entire passage benefited from advanced rail works as well as electrical and ventilation systems.

Tractor-trailer trucks carried out supply to the portals, of which two were discovered on the San Diego side. The portals were located out of sight in two warehouses approximately 800 feet (approx. 245m) apart.

Supply of the tunnels proved to be the Achilles heel of the trafficking operation. The DEA has revealed that agents flagged up the suspicious parking of one of the trucks outside a warehouse during routine surveillance. The truck was then halted at a traffic checkpoint in Temecula, USA and relieved of its 27,600lb (approx. 12,500kg) cargo of marijuana.

“This discovery again shows the cartels’ growing desperation in the face of beefed up border security and the costly extremes these organisations are trying in an effort to avoid detection,” said Miguel Unzueta, special agent in charge of security investigations in San Diego. “Once again, we’ve thwarted their scheme and I predict you’ll see more such successes in the future.”

In the last four years, more than 75 smuggling tunnels have been detected traversing the border, most of which emerge in California and Arizona.