Mexican police reveal cross-border drug tunnel Reuters

US and Mexican authorities have found one of the most sophisticated secret drug-smuggling tunnels ever discovered on their shared border.

An estimated 17 tonnes of marijuana were found in the tunnel, which is about 400 metres long and linked warehouses in San Diego and Tijuana, authorities said.

US authorities seized about nine tonnes of marijuana inside a truck and at the warehouse in San Diego's Otay Mesa area, said Derek Benner, US immigration and customs enforcement special agent in charge of investigations in San Diego. Mexican authorities found about eight tonnes south of the border.

They made the announcement at a news conference near packages of seized drugs festooned with labels of Captain America, Sprite and Bud Light. The markings are codes to identify the owners.

Photographs taken by Mexican authorities show an entry blocked by bundles that were likely to be stuffed with marijuana, said Paul Beeson, chief of the US border patrol's San Diego sector. Tunnel walls were lined with wood supports. The passage was equipped with lighting and ventilation systems.

The tunnel was about 1.5 metres high and a metre wide.Two men allegedly seen leaving the warehouse in a truck packed with about three tonnes of marijuana were pulled over on Tuesday on a highway in the suburbs of La Mesa and arrested. A California highway patrol officer was overwhelmed by the smell, according to a federal complaint.

Cesar Beltran and Ruben Gomez each face a maximum penalty of life in prison if convicted of conspiracy to distribute marijuana, said Alana Robinson, chief of the US attorney's narcotics enforcement section in San Diego. They were scheduled to be arraigned on Thursday.

Cross-border tunnels have proliferated in recent years, but the latest find is one of the more significant, based on the amount of drugs seized.

Raids last November on two tunnels linking San Diego and Tijuana netted a combined 50 tonnes of marijuana on both sides of the border, two of the largest cannabis busts in US history. Those secret passages were lined with rail tracks, lighting and ventilation.

As US authorities tighten controls on land, tunnels have emerged as a significant way to smuggle marijuana. Smugglers also use single-engine wooden boats to ferry bales of marijuana up the US Pacific coast and pilot low-flying aircraft that look like motorised hang-gliders to make quick drops across the border.

More than 70 tunnels have been found on the border since October 2008, surpassing the number of discoveries in the previous six years. Many are clustered around San Diego, California's Imperial Valley and Nogales, Arizona.

California is popular because its clay-like soil is easy to dig with shovels. In Nogales, smugglers tap into vast underground drainage canals. Authorities said they found a drug tunnel on Tuesday in Nogales, running from a drain in Mexico to a rented house on the US side.

San Diego's Otay Mesa area has the added draw of plenty of warehouses on both sides of the border to conceal trucks being loaded with drugs. Its streets hum with trucks by day and fall silent on nights and weekends.

After last November's twin finds, US authorities launched a campaign to alert Otay Mesa warehouse landlords to warning signs. Landlords were told to look for construction equipment, piles of dirt, sounds of jackhammers and the scent of unburned marijuana.

US authorities linked the November finds to Mexico's Sinaloa cartel, headed by that country's most-wanted drug lord, Joaquin "El Chapo" Guzman. The cartel has expanded its sphere of influence to Tijuana in recent years.

US authorities said the sophistication of the latest tunnel suggested that a major Mexican drug cartel was involved, but no link had been established.