What lies beneath: lawmakers introduce tunnel legislation.

• Position: SECURITY BEAT: Homeland Defense Briefs

The movement of illegal immigrants or narcotics through a tunnel under a U.S. border is a felony, but there are no laws on the books preventing the excavation itself. Bipartisan legislation aiming to close this loophole has been introduced in both houses of Congress.

"Many people are astonished to learn that constructing tunnels across the border is not already illegal," said Sen. Jon Kyl, R-Ariz., who is co-sponsoring the bill along with Sen. Dianne Feinstein, D-Calif.

Eight tunnels have been discovered in the San Diego area since the beginning of this year. Forty have been found so far, with 39 along the southern border and one under the northern border.

Some are simple "gopher holes," only a few feet long near a fence. Others are sophisticated, well-engineered constructions replete with lights, pulleys, drainage and ventilation systems, and well-hidden entrances.

One of the largest was discovered near the Tijuana airport in January. Its entrance on the Mexican side was located under four tiles in a warehouse office. Law enforcement confiscated 2,000 pounds of marijuana on the Mexican side and 300 pounds on the U.S. side.

The bills will make it a federal violation to build or finance a tunnel. Judges could hand down sentences of up to 20 years. Those who "recklessly" allow a tunnel to be built on their property may face up to 10 fu years. The proposed law would also double sentences for those who use tunnels to smuggle aliens, contraband or terrorists.

Meanwhile, efforts continue to improve tunnel detection. Joint Task Force North, out of Fort Bliss, Texas, has a unit dedicated to applying technologies used in the...