(NewsNation) —An 1,800-foot tunnel connecting Tijuana, Mexico, with a warehouse near San Diego, California has been discovered by authorities, leading to the seizure of drugs and the arrest of suspected smugglers.

The tunnel, about the length of six football fields, was equipped with ventilation, a rail system and electricity.

Authorities seized 1,762 pounds of cocaine, 165 pounds of meth and 3.5 pounds of heroin in the tunnel. The drugs hold a total street value of more than $25 million.

Six southern California residents were charged with conspiracy to distribute cocaine.

“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.”

Surveillance of a known drug house near San Diego led authorities to a warehouse where no drugs were found, but a hole in the floor leading to the tunnel was.

A tight squeeze was needed for the smugglers to enter the tunnel through the passageway that was just four feet in diameter and extended six stories below the ground. The ceiling was too low in the tunnel for most people to stand up.

Dozens of tunnels have been discovered over the year connecting Mexico to California and Arizona. The Drug Enforcement Agency believes they are connected to the Sinaloa drug cartel. Authorities have found about 15 sophisticated tunnels on California’s border with Mexico since 2006.

Authorities did not link the latest tunnel to any specific cartel.

The National Border Patrol Council said some of the tunnels cost millions of dollars to construct.

Hard drugs, such as heroin, methamphetamine and fentanyl, are typically smuggled through official border crossings from Mexico because their small size and lack of odor make them difficult to detect. But tunnels give smugglers an advantage of being able to carry huge loads at lightning speed.

After staking out the home that was recently used to stash drugs, officials began making traffic stops of vehicles that had been there or at a warehouse near the border, turning up boxes full of cocaine, according to a federal criminal complaint filed in San Diego.

They raided the properties — finding no other drugs at the warehouse, but a tunnel opening carved into the cement floor, federal prosecutors said.

Many tunnels, including the one announced Monday, are in San Diego’s Otay Mesa industrial area, where claylike soil is conducive to digging and warehouses provide cover.

By federal law, U.S. authorities must fill the U.S. side of tunnels with concrete after they are discovered.