Immigration officials have busted a drug-smuggling ring that was in the process of getting off...or under...the ground.  A border tunnel discovered Thursday is just one of what officials say are increasingly sophisticated attempts to get drugs into the U.S.

FOX News Radio's Jessica Rosenthal reports in our ongoing series on national security:

Securing America.

An unfinished tunnel discovered by Mexican authorities under a warehouse bathroom in Tijuana had ventilation and electricity.

Immigration-Customs Enforcement spokeswoman Lauren Mack says smugglers still rely on tunnels as a means of getting products into the U.S.  She says in the last two Novembers, two tunnels were discovered in the border area shared with San Diego.

(Mack) "The agents link the timing to the end of the harvest season, where the drug cartels try to get their marijuana out of their warehouses and into the U.S. before the year ends."

She says their goal is to get inside organizations to identify and take down the people behind the financing and architecture of these tunnels.

Jessica Rosenthal, FOX News Radio.