LOS ANGELES, CA (Catholic Online) - The transactions cost one American quarter. The parking meters on International Street, which hugs the border fence in Nogales, cost 25 cents. Smugglers in Mexico tunneled under the fence and under spaces and then carefully cut neat rectangles out of the pavement.

Smugglers on the U.S. side would park false-bottomed vehicles in the spaces above the holes, pay their quarter, and then wait while the smugglers stuffed their cars full of drugs from below.

Smugglers would then use jacks to put the pavement "plugs" back into position. The car would drive away. Only the keenest observers would notice the seams in the street.

U.S. Border Patrol agents found 16 tunnels leading to the 18 metered parking spaces on International Street. The pavement is now riddled with neat, symmetrical patches.

"It's unbelievable," Nogales mayor Arturo Garino told television reporters. "Those are the strides these people take to get the drugs across the border."

Past methods of smuggling have included catapults that launch bales of drugs across the border fence. "The [smugglers] have tried everything," Garino says, "And this is one of the most ingenious [methods] of them all.

The city, advised by Homeland Security, has agreed to remove the parking meters. Nogales stands to lose $8,500 annually in parking revenue, plus the cost of citations.

Mexican cartels have traditionally used planes, boats and human backpackers to ship narcotics to the U.S. market. Crackdowns in Mexico have fueled a violent, four-year drug war there. A longer border fence and more robust US border patrols, may be leading cartels to increasingly focus their transportation routes on tunnels, authorities warn.

"The [tunnel-building] activity levels have been skyrocketing. It has to do with all the new border security," U.S. Immigration and Customers Enforcement (ICE) agent Jose Garcia said.

Though the tunnels range from large concrete-reinforced passages to small hand-dug crawlways, most represent a significant investment by cartels in time and money, with some tunnels estimated to have cost millions of dollars to build.

"The tunnel is basically is the proverbial golden goose that can continue to lay golden eggs if it is completed," Tim Dunst of the San Diego Tunnel Task Force told television reporters.

© 2011, Catholic Online. Distributed by NEWS CONSORTIUM.