SAN DIEGO – An estimated 17 tons of marijuana were seized after the discovery of a cross-border tunnel that authorities said Wednesday was one of the most significant secret drug smuggling passages ever found on the U.S.-Mexico border.

The tunnel, discovered Tuesday, stretched about 400 yards and linked warehouses in San Diego and Tijuana, authorities said. 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, U.S. Immigration and Customs Enforcement 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. The passage was equipped with lighting and ventilation systems.

The tunnel was about 4 feet high and 3 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 in suburban 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 U.S. attorney’s narcotics enforcement section in San Diego. They are scheduled to be arraigned today.

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 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.