Mexican drug cartel tunnels into California

Customs officials find a sophisticated smuggling operation that led straight into San Diego

Investigators suspect a major drug cartel was the driving force behind two long, sophisticated tunnels connecting Mexico with the US that have been discovered, along with more than 40 tons of cannabis. Both are 2,000ft long, run from Mexico to San Diego and are equipped with lighting, ventilation and a rail system for drugs to be carried on a small cart.

The tunnels are believed to be the work of Mexico's Sinaloa cartel, headed by that country's most wanted drug lord, Joaquin "El Chapo" Guzman, said Mike Unzueta, the head of investigations at US Immigration and Customs Enforcement in San Diego. "We think ultimately they are controlled by the same overall cartel but the tunnels were being managed and run independently by different cells operating within the same organisation," Mr Unzueta said.

The tunnel found on Thursday extends from the kitchen of a home in Tijuana, Mexico, to two warehouses in San Diego's Otay Mesa industrial district. Three men were arrested in the US, and the Mexican military raided a ranch in Mexico and made five arrests in connection with the tunnel. American authorities have discovered more than 125 clandestine tunnels along the Mexican border since the early 1990s, though many were crudely made and incomplete.

The passage found Thursday is one of the most sophisticated to date, with an entry shaft in Mexico lined with breezeblocks and a rail system. US authorities do not know how long the latest tunnel was operating. Mr Unzueta said investigators began to look into it in June after a tip-off which emerged from a large drugs bust of cannabis, cocaine and methamphethamine by the San Bernardino county sheriff's department.

American authorities followed a tractor-trailer (articulated lorry) from one of the warehouses to a border patrol checkpoint in Temecula, where they seized 27,600lb of cannabis. The driver, whose name was not released, was arrested, along with two others who went to a residence in suburban El Cajon that had $13,500 (£8,660) in cash inside. "That trailer was literally filled top to bottom, front to back," said Mr Unzueta. "There wasn't any room for anything else in that tractor-trailer but air."

Three tons of cannabis were found in a "subterranean room" and elsewhere in the tunnel on the US side. Mexican officials seized four tons of cannabis at a ranch in northern Mexico, bringing the total haul to more than 20 tons.

The discovery of the other cross-border tunnel earlier this month marked one of the largest cannabis seizures in the US, with agents confiscating 20 tons of the drug they said were smuggled through the underground passage. That tunnel ran for more than 2,000ft under the border and warehouses in Mexico and San Diego. One of the warehouses involved in the tunnel discovered Thursday is only a half-block away.

In Thursday's discovery, the tunnel's breezeblock-lined entry in Mexico dropped 80ft to 90ft to a wood-lined floor, Mr Unzueta said. From the US side, there was a stairway leading to a room about 50ft underground that was full of cannabis. "It's a lot like how the ancient Egyptians buried the kings and queens," he said.