The discovery of a secret drug smuggling passage that stretched about 400 yards and linked warehouses in San Diego and Tijuana has lead to the seizure of an estimated 17 tons of marijuana, in what authorities say is one of the most significant narco-tunnels ever found.

U.S. authorities seized about nine tons of marijuana inside a truck and at the warehouse in San Diego's Otay Mesa area, said Derek Benner, the U.S. Immigration and Customs Enforcement (ICE) special agent in charge of investigations in San Diego. Mexican authorities recovered about eight tons south of the border.Authorities spoke at a news conference near packages of seized dope festooned with labels of Captain America, Sprite and Bud Light. The markings are codes to identify the owners.

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

The tunnel was about four feet high and three feet wide. It dropped about 20 feet on the U.S. side.

Two men allegedly seen leaving the warehouse in a truck packed with about three tons of pot were pulled over Tuesday on a highway and arrested. A California Highway Patrol officer was overwhelmed by the smell of the drugs, according to a federal complaint.

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

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

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

As U.S. authorities tighten their noose on land, tunnels have emerged as a major tack to smuggle marijuana. Smugglers also use single-engine wooden boats to ferry bales of marijuana up the Pacific Coast and pilot low-flying aircraft that look like motorized hang gliders to make lightning-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, Ariz.

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

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

After last November's twin finds, U.S. 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.

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

U.S. authorities said the sophistication of the latest tunnel suggests that a major Mexican drug cartel was involved, but no link has been established.

Based on reporting by the Associated Press.

U.S. authorities find drug tunnel on Arizona border

U.S. Immigration and Customs Enforcement announced Wednesday the discovery of a new "narco-tunnel" in the Arizona border city of Nogales.

Kevin Kelly, special ICE agent in charge of the investigation in Nogales, told Efe that the underground passage was found leading into Mexico from a rented house less than two miles west of the Dennis DeConcini Port of Entry.

He said that the drug tunnel was used to smuggle marijuana into the United States.  ICE agents executed a search warrant on the property on Tuesday and discovered the tunnel hidden under the house.

U.S. Border Patrol agents and Mexican authorities followed the tunnel and found that it was approximately 70 feet long and terminated in Mexico.

The tunnel was approximately three feet wide and two feet high, but it did not follow a straight line, given that some portions were at a greater depth than others and it was in the shape of a 90-degree curve.

The tunnel ends in the sewer system running underneath Nogales, Mexico.

Kelly said that authorities suspect that the drug was smuggled through the tunnel and then loaded into cars that had been parked in front of the house.

Based on reporting by EFE.

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