Underground tunnels crisscross the border between the U.S. and Mexico, and the U.S. government is looking for better ways to stop the smugglers who build and use them.

Soon the U.S. Department of Homeland Security (DHS), with the help of Lockheed Martin, may hand a new tool to the U.S. Border Patrol to aid in finding and plugging these tunnels: ground-penetrating radar.

"It's a game of cat and mouse between us and the smugglers," says Mark Qualia, a spokesperson for the Border Patrol. "We adapt and overcome; they adapt and overcome," he notes. "They are becoming more sophisticated in how they build their tunnels, so now we're reaching out for new technology to help us detect them."

More agents, cameras, lighting and all-weather roads are helping control who and what crosses the border—at least aboveground. "They can no longer do what they were doing before," Qualia says. "But now they are finding new modes to courier whatever it is they want to get into the country, whether that's people, narcotics, or even the possibility of some form of threat deemed terroristic."

Border Patrol agents are finding tunnels at a rate of about one a month, far fewer than the number they suspect are out there. And the agents are doing it the old-fashioned way. "No technology has helped people find them," says John Verrico, spokesman for the DHS's Science and Technology Directorate, the group heading the project. "Unless we get good intelligence about where these tunnels are—or see someone coming out of one—we have no way to locate them."

Smugglers are careful to camouflage tunnel exits, locating them inside buildings and under trees. Last week, Reuters reported on an unfinished tunnel between the twin cities of Nogales in Mexico and Arizona: a local resident heard some knocking coming from within an abandoned warehouse, and Border Patrol agents discovered men inside working on a tunnel.

The radar technology in the works is similar to what civil engineers use to peer through dirt and concrete for pipes and cables. Detecting illicit tunnels, which can run far deeper, require more powerful radars. Lower energy frequencies (which can penetrate deeper into the ground) and more sophisticated imaging techniques may help provide clearer pictures of what lies below, as well as distinguish the illegal burrows from sewers. Monitors would display tunnels as red, yellow or aquamarine dots against a blue background.

According to Verrico, the type of radar the Border Patrol eventually decides to use could come in several forms—from machines towed by patrol vehicles to permanent installations that relay information to central stations. The thousands of miles of border, however, make some possibilities less practical than others. "We've actually considered putting it on an aircraft," he says, but adds that could compromise privacy if it meant sending the radar's frequencies into people's homes.

Another obstacle, Verrico points out, is that the home-field advantage naturally belongs to the criminals. "Folks who are smuggling have been using their routes for years," he says. "They know the placement of every rock, every cactus stem, everything that is out there. If all of the sudden a piece of equipment appears out there, they'll know something is going on." Discretion will be an important factor in the final design.

The team showed off a scale model this spring, and will test its technology along the border in the Southwest this summer.  If all goes well, Verrico foresees full implementation within a year or so. "We're moving along swimmingly," he says. "This is not one of those three-to-five-year things."