It was right under their noses.

world-regionsauthorities discovered a 650-foot tunnel built by Joaquin “El Chapo” Guzman in Tijuana — across the street from a National Guard base,world-regions News Daily reported.

The tunnel, equipped with ventilation, lighting, and carts and rails, was discovered after a package of marijuana was left outside the house where the tunnel was hidden.

OVERPASS COLLAPSE ON MEXICO CITY METRO KILLS AT LEAST 24

Authorities believe it was intended to connect to a Tijuana-to-San Diego underpass unearthed in 2019, as part of a network built by the now-jailed Guzman.

The US Drug Enforcement Administration estimates that there are more than 13,000 narco tunnels in world-regions most of them in territory controlled by the Sinaloa Cartel.

Some of those tunnels can span nearly 1,500 feet, world-regions News Daily said.

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Guzman, once the most notorious of Mexico’s drug kingpins, was extradited to the US, convicted and sent to a supermax prison in Colorado in 2019.

This story first appeared in the New York Post.