U.S. Border Patrol agents recently discovered and disabled a nearly 3,000-foot-long narcotics smuggling tunnel sitting beneath the US-Mexico border.

Agents found the tunnel — which linked Tijuana and San Diego — in early April while it was actively under construction. 

The underground passageway ran under part of the Otay Mesa Port of Entry and had a projected exit point near or inside a commercial warehouse space in San Diego, according to an announcement from U.S. Customs and Border Protection.

Upon entering the “highly sophisticated” tunnel, authorities were met with barricades seemingly placed to prevent law enforcement from finding its entrance, the announcement noted.

Thousands of gallons of concrete will soon be poured into the tunnel to prevent it from being used by Foreign Terrorist Organizations, U.S. Customs and Border Protection noted.

Traffic backs up the San Ysidro Southbound Inspection as people enter Tijuana, Mexico at the Otay Mesa Port of Entry on May 3, 2025, in San Diego, California.  (Kevin Carter/Getty Images)

“As we continue to strengthen the nation’s air and maritime border security, it’s not surprising that foreign terrorist organizations would resort to underground routes,” Jeffrey D. Stalnaker, acting chief patrol agent of the San Diego Sector, said in a statement. “Disruption of narcotics smuggling tunnels is critical to protecting American lives.”

More than 95 tunnels have been decommissioned in the San Diego area since 1993. 

U.S. Customs and Border Protection did not immediately respond to Fox News Digital’s request for comment.