With the discovery of four sophisticated tunnels in Otay Mesa over the past two years, agents with Immigration and Customs Enforcement have linked marijuana's summertime harvest season to the month of November.
“By September it's been packaged and ready to be pushed out. So we were seeing it by November, [that’s] when it’s coming through," said Joe Garcia, Deputy Special Agent in charge of ICE Homeland Security Investigations.
NBC San Diego took a trip back to where a 600-yard border tunnel was discovered on Thanksgiving Day back in 2010. While things have been quiet this November, Garcia says the Sinaloa Cartel, is still hard at work.
Video showed a demonstration of a heavy duty horizontal directional drill.
According to ICE, the drill is the latest gadget the cartel has been using to try and dig passages to send drugs across the border into the U.S. The machine is traditionally used to lay underground tubing.
“If you have a 10-inch or a 12-inch you can get a package through there. And put in on a pulley system and you could pull it thru, “ said Garcia.
ICE showed photos where they confiscated the machine in two separate attempts near El Centro last summer.
One was found hidden in a house, while the other was stashed in an abandoned supermarket.
Although both attempts were unsuccessful, according to ICE, one tunnel was at least a quarter-mile long.
"We don't believe we've stopped this threat,” explained Garcia. “This is a very viable threat for the cartels to use."
With history having a tendency to repeat itself, Garcia and his team are not taking any chances.
“You need to be patient, you need to be diligent and you need to be tenacious, “ he said.
A total of 52 tons of marijuana were found between the two tunnels discovered last November.
More than 70 passages have been found along the U.S. Mexico border in the last four years.