ARTHUR H. ROTSTEIN
The Associated Press

NOGALES - A thick underground concrete barrier built to block smuggling tunnels along a stretch of the border with Mexico in downtown Nogales has done the trick so far, a Border Patrol spokesman said Friday.
A private contractor built the 12-foot deep underground wall in four days last month, spanning 100 yards of the border just west of the DeConcini Port of Entry, the main downtown port between Nogales and its sister city, Nogales, Mexico.
A cross-border drainage system, the Grand Tunnel, runs north through both cities and beneath the port of entry under Grand Avenue, a main street in Nogales, Ariz.
Just a few feet south of the border the underground drainage canal turns west, running parallel to the 10- to 12-foot tall fence of corrugated steel - built from World War II surplus landing mats.
The drainage system that extends beneath the port long has been used by illegal immigrants trying to sneak into the country. But the portion south of and parallel to the border fence has become popular with drug smugglers.
In recent years, they have taken to digging crude tunnels that run a short distance north, crossing beneath the border fence.
The reinforced concrete structure, which spokesman Omar Candelaria said is about 1 1/2 to 2 feet thick, was installed to stop the tunnel-diggers.
"Organizations were breaking out of the main tunnel and digging 5 feet and going north," Candelaria said. "The barrier was built to the west of the port in the area where we've had most of our tunnels."
No tunnels have been found in the area since the barrier was put in place, he said.
Candelaria said patrol officials are evaluating how the barrier works, but have no plans yet for expanding it elsewhere along the drainage system in Nogales.
"As we get better, they (smuggling organizations) look to different alternatives to get their product across the border, and the Border Patrol is always looking for ways to make sure that we keep that stuff out of the United States," he said.