AUDIE CORNISH, HOST:
This is WEEKEND EDITION from NPR News. I'm Audie Cornish. Last week, the Homeland Security Investigations unit made a major find, more than 30 tons of marijuana in an underground tunnel linking warehouses in San Diego, California and Tijuana, Mexico. It's one of the largest pot busts in U.S. history and the most marijuana found in connection with an underground tunnel. In recent years, law enforcement officials have discovered more and more of these tunnels and some have taken notice of the fact that those discoveries seem to pick up before the holidays.
For more, we're speaking with Derek Benner. He's a special agent in charge of Homeland Security Investigations in San Diego. Mr. Benner, welcome to the program.
DEREK BENNER: Oh, thank you. Happy to be here.
CORNISH: Mr. Benner, describe what you found in this most recent tunnel and how elaborate it is because I've heard they can have electricity and railing and how complicated can they get?
BENNER: This particular tunnel was an amazing find for us and for law enforcement. It definitely is the most elaborate and sophisticated tunnel that we have ever seen here in the California-Mexico border region. And really what makes it elaborate is the fact that it was equipped with so many conveniences; the rail system used an electric cart to move the product through the tunnel. A hydraulic elevator system at the entry point to move the large amount of narcotics into the tunnel and onto the rail system and also provided for concealment of the entry point in the warehouse in Mexico.
CORNISH: We've read that the discovery of the tunnels by law enforcement officials seems to ramp up towards the end of the year. What about this theory that it is seasonal?
BENNER: We believe there is a seasonal trend similar to any business enterprise where the bottom line is profit, whether it's legitimate or illegitimate; that the cartels plan on having a certain amount of inventory at a certain point in the year. Clearly, after a harvest season is when their inventory reaches its maximum. Like any retailer, any business, it's imperative that they find ways to distribute their inventory and get the return on their investment.
CORNISH: What are the conditions that make these areas around San Diego, the Imperial Valley in California, actually good for digging.
BENNER: Two things in particular here in San Diego. One, is the type of soil that we find in the Otay Mesa area, which tends to be more of a clay-based sand and rock that really lends itself well to carving out tunnels. The second part is that Otay Mesa is an industrial warehouse area so there are warehouses on both sides of the border. You would normally see a lot of truck traffic and commercial traffic there. So it provides relatively good cover to make it look like this would be a normal course of business.
CORNISH: How much of this has to do with the fact that there's increased security above ground on the U.S.-Mexico border?
BENNER: It has a lot to do with it. Clearly, the hardening of the border has a big impact on the cartels and their ability to move their narcotics and it really forces the cartels to make significant investments in the tunnels, for example, and other routes and methods that normally may not have been considered in the past.
CORNISH: That's Derek Benner. He's U.S. Immigration and Customs Enforcement's special agent in charge of investigations in San Diego. Derek Benner, thank you so much.
BENNER: Thank you. Transcript provided by NPR, Copyright NPR.