Contraband: Seized at the Border

A driver claims he buys used cars over the border to import into the U.S., but an X-ray reveals something suspicious in his spare tire; when a traveler returning from Mexico declares snacks at Customs, a Fish and Wildlife expert is called in.

An officer suspects a car is carrying more than innocent Santeria sprays.

Officers find an 18-wheeler carrying more than a load of takeout containers. A couple raises suspicion after declaring bulldog semen, but the labeling suggests the box may actually contain stallion semen -- a valuable and tightly regulated substace.

During his first day on the job, a rookie officer relies on his training, sending a hesitant driver for further inspection -- and his hunch pays off. When a traveler claims to be visiting his dentist bimonthly in Mexico, officers investigate further.

A traveler is caught with blades for cockfighting, a cartel-run blood sport. Every year, Mexico grows millions of dollars of flowers for the U.S., but cartels are taking advantage of the influx of shipments during major holidays.

Two men arrive in an SUV carrying enough suitcases for an entire family. Officers discover it's no family car -- it's a Kevlar-lined, bulletproof tank, the type that the cartels use to transport high-ranking gang mambers and attack law enforcement.

Cartels hope CBP won't inspect happy families, but officers know not to fall for that smuggling trick. Due to avian flu, live chickens can't be brought into the U.S.

Each year, CBP recovers over 1,300 stolen vehicles at ports of entry. Many are heading to the black market, while cartels use others for trafficking. When officers receive a be on the lookout (BOLO) alert for a luxury car, they take it seriously.

Tourist Day attracts those who move south for the winter. Officers prepare for smugglers hiding inside crowds and parties fueled by alcohol and drugs.

Officers are caught off guard when a high-end sports car arrives at the border packing heat. At the bus terminal, a K9 alerts to a traveler's luggage. Upon investigation, officers find photographs showing large amounts of cash on her phone.

Customs and Border Protection forms one of the world's largest law enforcement agencies, drawing officers from many backgrounds. From rookies starting out, to veterans who have seen it all: at America's borders, the mission comes first for CBP officers.

Officers are caught off guard wen a high-end sports car arrives at the border packing heat. At the bus terminal, a K9 alerts to a traveler's luggage. Upon investigation, officers find photographs showing large amounts of cash on her phone.

While some officers have years of experience, others are stepping up for the first time -- fresh out of training, and ready to prove themselves. Because at the border, a rookie's first day could be a smugglers's last chance.

Every year, CBP officers process thousands of vehicles. Some look ordinary, and other are built to deceive -- because at the border, four wheels and an engine could be a cover for contraband.

Each year, CBP officers inspect thousands of animals, including family pets and exotic wildlife -- because at the border, the threat may come from a different species. Some look innocent, while others carry hidden dangers.

Millions of travelers cross the U.S. borders every year. And while some are innocent couples, others are partners in crime. Because at the border, love isn't always what it seems.

Drug cartels are estimated to control up to one-third of Mexico's territory -- there's an insatiable demand for guns and ammo south of the border, and a ready supply of Americans willing to smuggle them. CBP is ready to intercept.

As they pursue profit, drug cartels are constantly adapting -- hiding deadly narcotics where few would ever expect to find them.

Mexican cartels earn up to $40 billion annually from trafficking drugs like cocaine, fentanyl and meth into the U.S.