NOGALES, Ariz. -- Interstate 19 is the most direct route from Mexico to the Phoenix metropolitan area, making it one of the U.S. Border Patrol's last lines of defense against smugglers.

• Watch: Border Patrol: Checkpoint

Agents at the route's interim checkpoint, which is between Nogales, Ariz., and Tucson, have high-tech equipment that can spot dirty bombs and X-ray vehicles to find hidden drugs and people.

One piece of equipment is known as a "Z Backscatter Van," or ZBV, and was deployed in February. It uses the same high-quality X-ray technology as new, controversial airport security checkpoints.

The $750,000 mobile device, when loaded on a Ford F-350 pickup like a camper shell -- can scan any vehicle, including semitrailer trucks -- in minutes.

The ZBV can detect explosives, plastic weapons, nuclear, radioactive or organic threats -- as well as drugs.

Because of technology like this, smugglers go to great lengths to avoid this checkpoint, according to agent Mike Scioli.

"Ideally, smugglers want to get rid of their cargo -- whether it's humans or narcotics -- as fast as possible," he said.

Some illegal immigrants who want to avoid the checkpoint will jump off speeding trains or use branches to brush away their footprints.

Others try to slip through undetected during a shift change.

The checkpoint itself has become a point of contention. Local residents don't like it; however, border agents want to make it permanent.

E-mail reporter Tammy Leitner at Tammy.Leitner@kpho.com.