drug smuggling tunnel the length of six football fields was found by U.S. authorities running from Tijuana, Mexico to a warehouse in San Diego.

The secret entrance was located by San Diego’s Otay Mesa border crossing and featured rail and ventilation systems, electricity, and reinforced walls, per authorities.

During a Monday announcement, it was revealed that 1,762 pounds of cocaine, 165 pounds of meth and 3.5 pounds of heroin were seized during the investigation and that it was unclear how long the tunnel was running for, CBS News reports. Six Southern California residents have since been charged with conspiring to distribute cocaine.

The newly discovered tunnel is four feet in diameter and about six stories deep, and runs for one-third of a mile, giving smugglers an advantage in carrying over larger loads of drugs. Since 2006, authorities have discovered 15 tunnels on California’s border with Mexico. After these types of entrances are discovered, the U.S. side of tunnels have to be filled with concrete.

“There is no more light at the end of this narco-tunnel,” said Randy Grossman, U.S. Attorney for the Southern District of California. “We will take down every subterranean smuggling route we find to keep illicit drugs from reaching our streets and destroying our families and communities.”

The arrests related to the tunnel were much different than a smuggling arrest back in February, when a California man was caught trying to smuggle dozens of reptiles from Mexico into the U.S. 30-year-old Jose Manuel Perez allegedly told customs at the time that the reptiles “were his pets,” after he was found with approximately 60 critters.