Updated

The recently discovered “super tunnel” used by drug kingpins to smuggle drugs from Tijuana to San Diego may be the most sophisticated yet, but it is only one of a staggering 140 passageways under the Mexican border to have been found since 1990.

The 600-yard tunnel, which ran as deep as 35 feet beneath the surface, was equipped with lighting, ventilation and an electric rail system. Although authorities will fill it in from its U.S. terminus in a San Diego-area industrial park, experts say that won’t stem the underground tide of drugs and immigrants.

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"Tunnels are definitely the new paradigm for smuggling organizations who have to adjust to the constriction caused by border security strategies and the residual circumstances of a chaotic border," said Victor Manjarrez, associate director of the National Center for Border Security & Immigration at the University of Texas-El Paso.

Federal agents netted more than $10 million in marijuana and cocaine after finding the tunnel by watching a suspicious truck. Since 1990, more than 140 tunnels have been discovered mostly on the southwest border of the United States, according to a 2012 Department of Homeland Security Office of the Inspector General report, with an 80 percent increase in tunnel activity occurring since 2008.

Better security above ground is driving criminals to dig their way in, said Manjarrez, who has seen firsthand the trends in smuggling after a 20-year career with the U.S. Border Patrol, where he commanded the busy Tucson, Ariz., and El Paso, Texas, sectors.

“It is clear to me that the increased tunnel activity is a direct result of increased and improved border security efforts along the southwest border," Manjarrez said. “These tunnels absolutely add to the complexity of border security. The majority of Border Patrol sectors don’t have adequate mapping of existing and new tunnel systems."

Tristen Reed, Mexico security analyst for STRATFOR, a private intelligence firm based in Texas, said tunnels such as this are a reminder that the border isn't a real obstacle for smugglers, and that it's one of many ways both human and drug traffickers can operate.

“What's particularly concerning is that above ground, smugglers can only transport what can be concealed among legitimate goods or carried across expansive terrain,” Reed said. “With rail systems and ventilation in tunnels directly entering populated areas, smugglers can transport anything they want with less focus on concealment.”

The Otay Mesa area, where the so-called “super tunnel” was found, has seen major tunnel operations shut down over the past 20 years. Two of the largest marijuana seizures came from tunnels in this area. In November 2010, agents seized about 22 tons of marijuana from a tunnel there. A year later another 32 tons of marijuana from another tunnel in the area was also seized.

Police were led to this recent tunnel after a Chula Vista police officer pulled over a truck for a traffic violation where they found approximately three tons of marijuana in the back. The truck had been under surveillance leading investigators to a warehouse in Chula Vista which was allegedly being used as a drug transport center.

“The cartels have spent years and tens of millions of dollars trying in vain to create an underworld of secret passageways to move huge quantities of drugs at will,” U.S. Attorney Laura Duffy said. “We have a message for the builders, financiers and operators of these sophisticated tunnels: if you continue to go underground, you will find your world collapsing around you.”

Tunnels aren’t a new trend in smuggling, but the majority of those found recently have been well after the construction phase was completed leaving investigators to wonder what or who has been smuggled into the U.S.

“We have seen increased sophistication in construction of the tunnels in recent years -- tunnels which are built with rail systems and ventilation,” Reed said. “The improved designs certainly cost more money to construct, so that trend is a sign that smugglers see underground routes as a good investment with little risk.”

When U.S. authorities find smuggling tunnels, they typically block or fill them in from the U.S. side. Manjarrez warned the optimism of closing one major tunnel down should be tempered by the fact that there may be dozens, if not hundreds more. His center hopes to map the network of known smuggling tunnels, as well as old mining tunnels, sewer and water systems, and even old underground routes that were used for smuggling liquor during prohibition that are not mapped by DHS.