U.S. authorities have uncovered a sophisticated underground tunnel running beneath the U.S.-Mexico border that was allegedly used to smuggle more than $45 million into the U.S. and seize 1,000 kilograms of cocaine.

The tunnel stretched from the Mexican city of Tijuana to a retail store in California's Otay Mesa Port of Entry area. According to investigators, the passage was around 590 metres long and reached a depth of 16.8 metres underground. It measured up to 1.4 metres in height, allowing people and goods to move through it.

Authorities described the tunnel as highly advanced. It featured reinforced walls, a rail system, ventilation equipment, electricity supply, and a hydraulic lift that provided access. Video footage released by the U.S. Justice Department showed concrete steps leading into the tunnel. The passage appeared to have been carved through rock and had a concrete floor.

Federal drug investigators from Homeland Security spent several months monitoring activities around a retail outlet called “Buy 4 Less” on the U.S. side of the border. Officials closely watched the movement of individuals entering and leaving the store as part of the investigation.

When authorities carried out enforcement action, they discovered more than 1,000 kilograms of cocaine. Investigators believe the narcotics had been transported through the underground tunnel before being loaded onto trucks for further distribution.

Commenting on the discovery, Justin De La Torre, chief patrol agent for the Border Patrol’s San Diego sector, said, “Criminal organisations continue to look for ways to exploit our border, but they underestimate the determination of the men and women protecting it.”

He added, “This tunnel’s discovery is a testament to our strong partnerships and the unwavering commitment of law enforcement on both sides of the border.”

Four individuals have been charged in connection with the alleged drug-smuggling operation. The accused include two residents of San Diego and two Mexican nationals.

The Justice Department said the discovery highlights a long-standing challenge faced by law enforcement agencies in the region. Since 1993, authorities have found 99 underground passages in the Southern District of California. Among them, 28 were classified as sophisticated tunnels due to their advanced construction and features.

Officials noted that the last operational tunnel discovered in the area was found in 2022. The latest discovery is one of the most significant tunnel-related drug-smuggling cases uncovered in recent years and reflects the continued efforts of criminal groups to move narcotics across the border using increasingly complex methods.