In one of the most elaborate underground operations discovered in recent years, U.S. Border Patrol agents have disabled a massive drug smuggling tunnel stretching nearly 3,000 feet beneath the U.S.-Mexico border.

According to U.S. Customs and Border Protection (CBP), the tunnel — discovered in early April — originated in Tijuana, Mexico, and extended more than 2,918 feet into the Otay Mesa area of San Diego, California. Officials say the tunnel was still under construction when it was located by agents, who were acting on intelligence from the San Diego Sector Border Patrol’s Tunnel Team.

Measuring approximately 50 feet deep, 42 inches high, and 28 inches wide, the tunnel boasted an array of sophisticated infrastructure. It included ventilation systems, electrical wiring, lighting, and even a rail system designed to move narcotics efficiently across the border.

The route passed beneath a segment of the Otay Mesa Port of Entry and appeared to be on course to surface near — or possibly inside — a commercial warehouse, authorities said.

Agents also encountered makeshift barricades inside the tunnel — temporary obstructions seemingly placed to delay detection and obscure the passage’s origin.

This is not the first time drug traffickers have used underground tactics in this region. Since 1993, over 95 tunnels have been found in the San Diego area alone, making it one of the most active smuggling zones for subterranean drug transport in the U.S.

Officials say the newly discovered tunnel is scheduled for “immediate remediation.” Contractors have been dispatched to fill it with thousands of gallons of concrete to render it unusable — both by narcotics traffickers and any potential terror threats.

The full extent of the tunnel’s use remains under investigation. No arrests have been announced, and officials have not yet confirmed whether any contraband had already been successfully transported through the unfinished passage.

The tunnel was first reported by Fox 10 Phoenix and Fox 5 San Diego, both citing CBP and Border Patrol officials.