A drug smuggling “super tunnel” discovered by US officials is so sophisticated authorities have suggested that cartels have engineers and architects on the payroll.

The tunnel, which links warehouses in Tijuana, Mexico with San Diego, California, may have taken years to complete and vast sums of money to fund. It is fitted out with high-tech lighting, ventilation and an electric rail system.

“They’ve worked very hard over a year, maybe two years to build a tunnel of this sophistication. It’s taken hundreds of thousands of man hours and millions of dollars to complete,” said Bill Sherman of the Drug Enforcement Administration (DEA).

US Attorney Laura Duffy said the advanced designs would have needed input from experts who knew what they were doing.

“They are hi-tech, they include railways, push carts, ventilation systems, and hydraulically-controlled steel doors,” she said.

Tunneling was one of the earliest areas of application in the field of civil engineering. The ancient Egyptians built tunnels for transporting water and for use in tombs, as well as undertaking mining operations to extract copper ore.

But constructing a tunnel is also one the most complex challenges for civil engineers. Requiring both structural and geotechnical skills, the layout of the underground space, the excavation method, ventilation for air quality, safety procedures and the support system are all critical components requiring specialist consideration.

Drug Tunnel Tijuana 1

Cross Border Tunnel Connecting Mexico to USA

The Tijuana-San Diego tunnel goes well beyond being basic. Around four feet in height and three feet in width it zig-zags for about a third of a mile along the border at a depth of approximately 35 feet, according to Derek Benner of US Immigration and Customs.

An informant told officials that operators had brought drills and other construction equipment needed for tunnel construction earlier this year, which led to the surveillance of the San Diego warehouse.

This is the eighth such tunnel discovered in San Diego since 2006 as the cartels look for ways to get their product onto the streets as quickly as possible after the harvest months.

A 1,800-foot tunnel was discovered in November 2011, which resulted in the seizure of a total of 32 tonnes of marijuana.