|Officials discovered a tunnel which joined warehouses in Tijuana, Mexico, to Otay Mesa in southern California [Reuters]
US authorities say they have uncovered a "major" drug-smuggling tunnel under the US-Mexico border, the latest such find on the frontier.
US and Mexican officers seized on Tuesday at least 14 tonnes of marijuana and arrested two people linked to the "sophisticated" tunnel, which joined warehouses in Tijuana, Mexico, and Otay Mesa on the US side in southern California.
The 400-yard-long tunnel, complete with electricity and ventilation, was unearthed by the multi-agency San Diego Tunnel Task Force after authorities spotted a suspicious lorry leaving the Otay Mesa warehouse.
The US Immigration and Customs Enforcement (ICE) service described the find as a major victory over Mexican drug cartels responsible for vast trafficking across the border into to the US.
"The drug cartels mistakenly believe they can elude detection by taking their contraband underground, but, again and again, we've been able to find these tunnels and shut them down," Derek Benner, an ICE official, said on Wednesday.
Tuesday's operation began when highway police stopped the suspicious lorry and found three tonnes of marijuana. Two men were arrested and a warrant was issued to search the warehouse, where agents found another 6.5 tonnes of
"Inside the nondescript white building, investigators discovered the entrance to the passageway. From the warehouse floor, the tunnel plunges more than 20 feet to the bottom of the shaft," the ICE said.
"The passageway, measuring approximately four feet by three feet, is equipped with structural supports, electricity and ventilation."
The ICE said investigators believe the tunnel was only recently completed.
Mexican counterparts, alerted by the US side, entered the Tijuana warehouse and found five to six additional tonnes of marijuana.
The find was made by the San Diego Tunnel Task Force, which combines officers from agencies including ICE, US Customs and the Drug Enforcement Administration (DEA).
US authorities have detected more than 75 cross-border smuggling tunnels over the last four years, mostly in California and Arizona. The latest one is the sixth large-scale tunnel discovered in San Diego since 2006.
"The fact that this is the third sophisticated cross border tunnel found within a year's time demonstrates the cartels will stop at nothing to smuggle their drugs into the US," William Sherman, head of DEA San Diego, said.
"The seizure of marijuana coupled with the loss of yet another tunnel will deal a heavy blow to those responsible for constructing this tunnel.
On the Mexican side, General Gilberto Landeros Briseno said that 778 marijuana packets had been discovered inside the drug tunnel.
Some packets featured pictures of comic superhero Capitain America, which authorities believe to refer to "El Aquiles," a lieutenant of Joaquin "El Chapo" ("Shorty") Guzman, the billionaire Sinaloa cartel boss, Landeros Briseno said.
Mexican authorities have blocked off six cross border tunnels used for drug trafficking this year, including five in Tijuana, he said.
Mexico has seen a wave of unrest in recent years as powerful drug cartels have battled over lucrative trade routes to the US, with more than 45,000 people killed in drug-related violence since 2006.
That year Felipe Calderon, the Mexican president, launched a massive military crackdown, which critics say has led the cartels to develop more advanced tactics and more brutal methods without bringing security to border communities.