SAN DIEGO, Calif. (WFLA) — U.S. Border Patrol agents have recently discovered a vast tunnel they believe was used for large-scale drug smuggling.

The tunnel came to light in April when U.S. Customs and Border Protection agents in San Diego found it while it was still being built. Initial assessments indicated the tunnel’s exit was close to a commercial warehouse area.

Even while uncompleted, the tunnel stretched over 1,000 feet into the U.S.

CBP described it as “highly sophisticated,” complete with electrical wiring, lighting, ventilation systems, and a rail track for transporting goods.

The entire length of the tunnel spanned 2,918 feet, at some points reaching 50 feet underground. Certain sections were narrow, measuring only 42 inches in height and 28 inches in width, making it difficult for agents to navigate.

Last week, CBP, along with Homeland Security Investigations and the Mexican Government, located the tunnel’s entrance in a neighborhood in Nueva Tijuana. The entrance was inside a residence and had been concealed by freshly laid tile.

Now, thousands of pounds of concrete will be poured into the tunnel to prevent any further use.

CBP said that since 1993, 95 tunnels have been discovered in the San Diego area.