The just-discovered cross-border tunnel that authorities say was used as a major underground drug passage. (U.S. Immigration and Customs Enforcement/AP)

“It is clearly the most sophisticated, major tunnel that we have found in the last five years, perhaps ever,” said Lauren Mack, a spokeswoman for the U.S. Immigration and Customs Enforcement in San Diego, according to the Associated Press.

The tunnel, which is 2,200 feet long, the equivalent of more than seven football fields, was found in San Diego’s Otay Mesa area, and leads to a warehouse in Tijuana, according to authorities. The warehouse is on the same block as a federal police office. Marijuana was discovered in the new tunnel and Mack said federal agents would announce the amount, along with other details about the tunnel, at a press conference in San Diego at 5 p.m. ET.

The discovery comes after a finding two weeks ago of a sophisticated, well-lit and ventilated 400-yard passage linking warehouses in San Diego and Tijuana. U.S. authorities seized 17 tons of marijuana on both sides of the border after discovering the 400-yard tunnel.

More than 70 passageways have been found along the border since October 2008, marking a major increase over the previous six years. Many of those have been found in California, a popular location due its clay-like soil that’s easy to dig through. Otay Mesa, the location of the most recent tunnel, is a prime spot because of its plethora of warehouses that can easily conceal trucks getting loaded with drugs.

See photos of earlier tunnels found below:

A drug smuggling tunnel from Mexico uncovered by U.S. Border Patrol in Nogales, Ariz., is shown in this photograph released Nov. 22. The tunnel is 319 feet long and extends 219 feet into the U.S. and 100 feet into Mexico. It is about 20 feet below the surface and measures 3 feet wide by 2 feet tall. While securing the tunnel, Nogales Border Patrol agents also found 26 bundles of marijuana weighing more than 430 pounds and worth about $215,000. (Reuters)