U.S. authorities announced the discovery of a drug tunnel linking this city and neighboring Tijuana, Mexico, and the seizure of nearly 18 tons of marijuana.

The 400-yard-long tunnel had a ventilation system, the head of the Border Patrol's San Diego Sector, Paul A. Beeson, told a press conference.

The tunnel linked an unfinished building near Tijuana's international airport and a warehouse in the Otay Mesa area of San Diego.

The discovery was made by a multiagency tunnel task force comprising personnel from Immigration and Customs Enforcement, Customs and Border Protection and the Drug Enforcement Administration, ICE spokesperson Lauren Mack said.

Alerted by the U.S. task force, Mexican authorities quickly located the Tijuana end of the tunnel.

U.S. agents found six tons of marijuana inside the San Diego warehouse and three more tons aboard a truck they saw leave the building before the task force pounced.

The investigation led authorities to a marijuana farm east of San Diego, where they confiscated 204 plants and additional pot.

Some of the bundles of marijuana in the warehouse were labeled with images of the comic book character "Captain America," a logo associated with Tijuana-based trafficker Alfredo Arteaga Gonzalez.

More than 70 drug tunnels have been found along the U.S.-Mexico border in the last four years.