Washington, US federal authorities on Thursday confirmed the discovery of a tunnel, the longest cross-border passageway ever unearthed along California's border with Mexico, through which drugs were being smuggled. The 800-metre-long passageway extends from a house in Tijuana, Mexico, to a hole in a commercial lot in an Otay Mesa industrial park in California. The hole, measuring one metre in diameter, was hidden underneath a large industrial dumpster, EFE news reported. The sophisticated tunnel was equipped with lights, rails and a ventilation system, as well as an elevator from the passageway leading to a closet inside the house in Mexico, authorities said. As a result of the discovery, federal authorities took control of the tunnel and a parking lot where they planned to transfer nearly 6.356 tonnes of marijuana and over one tonne of cocaine, worth more than $22 million. "Marijuana is something we regularly see associated with these tunnels, but not cocaine. We believe this is the largest cocaine seizure ever associated with a cross-border tunnel," said US Attorney Laura Duffy. A seven-month US Border Patrol investigation resulted in the arrests of six people with suspected links to the drug transfer tunnel. The probe began when authorities detected suspicious activity, including vehicles entering and exiting the California lot late at night, as well as unusual commercial activities in the area. A Border Patrol spokeswoman said the drugs were transported in small packages so they could pass through the hole in the Otay Mesa lot. This is the third cross-border tunnel in Southern California that federal agents have discovered in recent weeks. In the past five years, they have unearthed more than 75 tunnels on California and Arizona borders.