SAN DIEGO - At the control room of a cross-border trucking company in Otay Mesa, south of San Diego, dispatchers spend their days talking over the radio with drivers and poring over computer screens, constantly monitoring the whereabouts and activities of their 150 trucks.
"We got it on the map every time a driver is moving, standing by, stop at a light or stuff like that," the operations manager said while zooming in and out of a digital map. "Exactly, we know where the truck is at."
The company president asked that we not identify the firm or its employees out of security concerns.
The company's offices on the United States side are smack up against the U.S.-Mexico border fence. It also has offices and a truck yard in Tijuana, Mexico.
The trucking firm is meticulous about security measures. All of its trucks are equipped with GPS monitors.
Exact routes for the trucks are established from a warehouse in Mexico to the customer in the U.S., and software tells dispatchers if a truck goes off that route, or stops for more than two minutes.
The firm even hires private investigators to follow trucks at random to make sure they're not involved in anything illicit.
"Is drug smuggling the major security risk?" I asked.
"Yes, that's the highest, highest, in our industry," the operations manager said.
Actually, the risks here are multiple.
Trucking companies have to be careful about who they're working for. A seemingly stand-up exporter could be sneaking drugs in shipments of, say, plastic toys.
Or a rogue company driver could be surreptitiously working for the cartels - or maybe forced to work for them.
These risks have grown along with an 80 percent increase in truck traffic at the U.S.-Mexico border since 1995, the year after the North American Free Trade Agreement went into effect.
This explosion in trade means more opportunities for drug smugglers to get their loads across the border undetected.
And while, at least at San Diego area border crossings, more drugs are detected in passenger cars, commercial trucks yield huge seizures - on average, more than 1,800 pounds of drugs per bust last year.
At the Otay Mesa commercial port of entry, U.S. Customs and Border Protection officers process more than 2,000 trucks a day. And border agents have seen drugs hidden in just about everything.
"In cans of jalapeños, in cans of cheese," said Joe Garcia, deputy special agent in charge for U.S. Immigration and Customs Enforcement's Homeland Security Investigations.
"You see it mixed in with fabric softener, or laundry detergent," he said.
Border agents at Otay Mesa first check a truck's manifest when it gets to the head of the line. The manifest tells the agent about the truck, who's driving it, and what it's carrying.
An agent may chat up a driver to make sure he or she doesn't seem nervous or shifty. Agents may send a truck to secondary inspection, where it could go through a giant x-ray machine or have its cargo offloaded.
Several hours after we visited the Otay Mesa cargo crossing recently, agents found 1,600 pounds of marijuana concealed in a shipment of limes.
If drugs do make it across the border, their likely first stop is Los Angeles.
"Los Angeles is really a transshipment point," said Steve Woodland, who leads the Southern California Drug Task Force for the U.S. Drug Enforcement Administration.
"We are centrally located to be able to push the narcotics from California in multiple directions," Woodland said.
Woodland helped dismantled a high volume drug ring in August. The smugglers brought meth, cocaine and heroin across the border in PVC pipes hidden inside the axles of big rig trucks.
During the two-and-half year investigation, law enforcement seized more than 2,400 pounds of meth - that's around 11 million doses.
According to the criminal complaint, the illegal shipments were coming across the border in Nogales, Ariz.
Back at the trucking company's yard in Otay Mesa, a security guard runs a large round mirror with a long handle underneath the perimeter of a truck to make sure there's nothing attached to the bottom.
The security guard also taps the truck's wheels with a baseball bat. Tires that have something hidden inside make a distinct sound.
The company's operations manager also tells me they do extensive background checks on their drivers.
"Especially if you're moving from one side to another, you gotta have security in everything," he said. "In every single little thing."
There's just too much at stake to take any risks, he said.