NOGALES - Nogales, Arizona, is notoriously known as a “tunnel city," utilized by traffickers to smuggle humans and narcotics into the United States. The U.S. Border Patrol and local authorities have responded with new technologies and a heavier presence in the area to help uncover and destroy the tunnels before they are completed.

Many of the migrants who embark north toward Arizona are fleeing the Border Patrol, not running toward them for help -- a stark contrast from the Texas border, where the vast majority of undocumented immigrants from Central America seek to be apprehended in a bid for asylum.

This is in part due to rampant human trafficking in the area, where smugglers called "coyotes" use immigrants to transport arms and narcotics across the border, and through tunnels underground.

Tunnel system

The U.S. Border Patrol granted Voice of America access to the 1.6-kilometer Morley drainage tunnel that runs north from Mexico into Nogales, Arizona. The tunnel originally was built to avoid flooding on U.S. territory, due to the higher elevation of its neighbor city, also called Nogales, across the Mexican border..

Kevin Hecht, a tunnel expert with the U.S. Border Patrol, explained, “So the gate's set up, when enough water pressure hits it, it hinges from the ceiling and it lifts up to let the water through, but it goes back down to keep the people out. And then that gate's in place too, there's one to the north, and the reason for that, is the smugglers would come in from the north, and mess with all this infrastructure, the lighting, the cameras and everything in here that monitors this, so we had to put gates on both sides.”

The preexisting drain and sewage infrastructure has created opportunities for drug traffickers to excavate and construct illicit border tunnels.

Nogales Mayor Arturo Garino praised efforts by the Border Patrol and police to halt construction of most tunnels and prevent them from ever being used. But he said he believes the tunnels will continue to be developed as long as the incentive remains.

“I wish there were tunnels for a subway system [laughs], but I think we're going to have tunnels forever, as long as there's a need, and as long as there's somebody in the United States that wants drugs, because that's why they come acrossm" he said. "They don't bring undocumented people through tunnels, they bring drugs.”

Tucson sector Border Patrol spokesman Pete Bidegain said agents maintain a heavy presence along the area's 48-kilometer border wall because of the smuggling activity, and they rely on cooperation with Mexican officials to keep the border secure.