Agents and officers work around the clock to secure the border between El Paso, Texas, and Ciudad Juarez, Mexico.

Along the El Paso-Juarez border, agents and officers of the Department of Homeland Security investigate a young couple who are suspected human smugglers, uncover a floor of marijuana in an SUV, and target a high-level supplier in a drug sting.

Drugs, guns, cars and money are just some of the items confiscated on a typical day by Customs and Border Protection (CBP). But what happens to this contraband after it is seized?

CBP agents dismantle an observation point used by smugglers to monitor agents' movements in the remote desert, and seize a vehicle attempting to carry weapons and nearly $800,000 back to the Mexican cartels.

In this episode of Border Wars, agents and officers struggle to stop cartels and illegal immigrants whove found weak spots in spite of increased fortification along the U.S.-Mexico Border. Four feet beneath Nogales, agents crawl through a claustrophobic drug smuggling tunnel, knowing they could come face to face with armed criminals. Near the Port of Entry, Nogales Rail Inspection Team is on high alert as a freight train full of new automobiles rumbles toward them. Trains, with infinite hiding places, are becoming a favorite place for cartels to stash drugs: If the officers arent careful, they could easily miss a load. In the desert, Border Patrols only dirt bike unit races after a group of illegal immigrants. But in this sprawling Indian Reservation, the agents will need skill - and luck - to catch them.

With the help of a Blackhawk helicopter, agents arrest a suspected smuggler who is backpacking drugs into the U.S.

Customs and Border Protection patrol the crucial boundary between El Paso, one of the safest cities in the U.S. and Cuidad Juarez, considered one of the most dangerous cities in the world.

Border agents in Arizona defend a national park overrun by smugglers.

Border agents in El Paso, Texas battle to secure the city from human trafficking and drug smuggling.

Agents chase smugglers in a dangerous high-speed pursuit.

Agents patrol the Rio Grande Valley in southernmost tip of South Texas. They catch drug smugglers burying contraband in tanker trucks and illegal immigrants sneaking around highway checkpoints in the middle of the night.

Agents persue a pickup truck loaded down with drugs ferried from Mexico; a routine vehicle inspection uncovers a large stash of heroin.

A search team races to rescue a mother and her son who were abandoned by smugglers in the brush.