COPS FIND 30 TONS OF WEED IN A MEXICAN DRUG TUNNEL!

United States border police involved in one of the largest drug busts in U.S. history discovered a 600-yard drug smuggling tunnel that was part of a sophisticated operation used to transport tons of marijuana between Mexico and southern California, authorities said Wednesday.

The tunnel was equipped with a rail system, lighting and air vents, stretching the length of six football fields underground between warehouses in Tijuana and the Otay Mesa area of San Diego, U.S. Customs and Border Protection said.

Agents discovered the passage this week during a massive seizure of about 30 tons of pot, which cops said had a street value of more than $20 million.

John Morton, director of the U.S. Immigration and Customs Enforcement Agency said both the tunnel and the massive stash were clearly linked to one of Mexico’s drug cartels, but it wasn’t clear which one.

"This wasn't a mom-and-pop operation,” Morton said. "This is clearly organized crime at work. This was the cartels."

The brutal gangs have been waging a bloody drug war along the U.S.-Mexico border that has killed about 30,000 people since 2006.

Officials said the bust started on Tuesday night when federal agents spotted a suspicious tractor-trailer leaving the San Diego warehouse and called the California Highway Patrol, according to The Associated Press.

California police stopped the rig and found 10 tons of pot inside the trailer. The driver, a U.S. citizen, and his Mexican wife were arrested.

Authorities then found the entrance to the tunnel during a search of the U.S. warehouse, where they recovered between 10 and 15 tons of pot, AP reported. Another five tons was found by Mexican soldiers in the tunnel and in the warehouse in Mexico.

The underground channel was about waist high – too low to stand up in but high enough to crawl through – and Morton said it was only in operation for a brief time.

Officials said the seizure was the largest in state history and believed to be the second largest in U.S. history, AP reported. A DEA sting involving 33 tons of pot in Oregon in 2008 is believed to be the largest marijuana bust in U.S. history.

In the past four years, 75 smuggling tunnels have been discovered on the border between the U.S. and Mexico, authorities told CNN. Nearly all of them connected Mexico to cities in California and Arizona.

About 125 tunnels have been found since the early 1990s, when authorities began keeping count.

In 2006, agents found an 800-yard tunnel running between Otay Mesa and Tijuana, the longest such tunnels discovered to date.