U.S. Border Patrol agents in Nogales, Arizona recently sealed a tunnel used by cartels to transport drugs and weapons from Mexico to the U.S.

According to the Latin Post, it took six trucks full of cement to seal the  tunnel on May 22. The underground passage was allegedly discovered in January. 

Reports state that the tunnel had air ducts, and that the top of it was about five feet underground. Police believe that vehicles loaded with narcotics regularly traveled through. 

The tunnel is apparently one of the biggest ever discovered by Border Patrol agents. It lead from a public parking near the border line lot to a residence in Nogales.

Sylvia Longmire, Breitbart Texas contributing editor and border security expert, said, “The main challenge with these drug tunnels continues to be how incredibly difficult they are to find. The level of sophistication of tunnel detection technology has increased over the last few years, but currently there is no one-size-fits-all solution that will work for the entire southwest border.”

She continued, “ICE and CBP agents must continue to rely on human sources, intelligence sharing, and investigative skills to detect tunnel construction–preferably before the tunnels are complete and fully in use.”

Kevin Hecht, a Border Patrol supervisor and coordinator who specializes in locating such tunnels, told the Latin Post, “Up until today, 173 tunnels have been discovered on the border between the United States and Mexico, 103 of those are in this city, under the supervision of the Nogales station, and total, 107 (the 103 plus another 4) are the responsibility of the Tucson sector.”

The cost of sealing up “narcotunnels” has not been disclosed to U.S. taxpayers.

“Drug tunnels are also the source of great expense for the US government, as it can cost several hundreds of thousands of dollars to seal just one with concrete,” Longmire said. “Their continued existence is a testament to the persistence and virtually unlimited funding of Mexican drug cartels.”

The Breitbart Texas team has reportedly extensively on narcotunnels. 

In November 2013, Breitbart Texas Managing Director Brandon Darby reportedly on one such massive smuggling tunnel under the border. “The tunnel stretched from a warehouse in Tijuana, Mexico to a building in a San Diego, California industrial park. It was complete with its own electric rail system, lighting, and ventilation systems,” Darby wrote. 

Then in April 2014, Darby reported on three additional discovered tunnels. 

He said that open areas of the 2,000 mile U.S.-Mexican border allow “only trickles of drug smuggling and human trafficking in comparison to the large scale single shipments that a tunnel[s] such as [these] make possible. There have also been recent cases of U.S. law enforcement accused of receiving payments to allow such shipments to cross the U.S./Mexico border.”

Follow Kristin Tate on Twitter @KristinBTate.