U.S. Border Patrol agents have uncovered a massive underground drug-smuggling tunnel stretching nearly 3,000 feet from a home in Tijuana, Mexico, to a warehouse in Otay Mesa, near San Diego, California, authorities confirmed this week.

The tunnel, which was still under construction when discovered in April, featured a high level of engineering sophistication. Officials reported the passage included electric wiring, lighting, a ventilation system, and even railsbelieved to be used for drug transport.

Measuring approximately 42 inches high, 28 inches wide, and descending 50 feet underground, the tunnel is believed to be the work of the Sinaloa Cartel, a powerful drug trafficking organization formerly led by Joaquín “El Chapo” Guzmán.

Although El Chapo is serving a life sentence in the U.S., the Sinaloa Cartel remains active and continues to operate smuggling routes across the U.S.–Mexico border.

Mexican authorities located the tunnel’s entrance beneath fresh tile flooring in a residence in the Nueva Tijuana neighborhood, raising concerns about how advanced the operation had become before being shut down.

“Stopping drug tunnels like this is vital to keeping Americans safe,” said Jeffrey Stalnaker, acting chief patrol agent for the San Diego sector. “Our team worked closely with Mexican law enforcement, and their cooperation was key to this discovery.”

The tunnel’s U.S. exit was located in an industrial warehouse district in Otay Mesa, a known hotbed for previous tunnel-related activity.

Since 1993, officials have discovered over 95 tunnels in the San Diego region alone, underscoring how frequently cartels attempt to bypass traditional border security. Each time a tunnel is found, U.S. authorities work to fill and seal it with concrete to ensure it can’t be reused.

In a related case earlier this year, officials also found a smaller tunnel in El Paso, Texas, running from Ciudad Juárezinto the city’s storm drain system. That tunnel had already been used for human smuggling, with some migrants reportedly paying up to $20,000 to make the dangerous underground journey.

As border authorities continue to tighten above-ground security, experts say smuggling organizations are becoming more reliant on sophisticated underground routes — a challenge that officials say requires constant surveillance, international coordination, and advanced detection technology.