Border Force: America's Gatekeepers

Officers in Hidalgo are forced to close the bridge when it's stormed by dozens of asylum seekers trying to jump the queue of people waiting to seek refuge in the USA.

The 2,000-mile border that separates Texas and Mexico is the busiest international boundary in the world. On the United States side, Customs and Border Protection officers have the job of keeping goods and people flowing in both directions while making sure that guns, drugs and other contraband don't make it across the border. The challenge is daunting: on one side is the ruthlessly-efficient Mexican drug cartels; on the other, the biggest - and most lucrative - drug market on earth. Borderforce: America's Gatekeepers follows CBP officers stationed at 12 of the 28 international bridges that straddle the border and documents the immense challenges that the officers face on a daily basis.

Officers in Progreso are on the lookout for day-trippers trying to smuggle prescription pills back into America, bought cheaply from one of the 200 pharmacies just on the other side of the border. At the Juarez Lincoln bridge a new recruit is waiting for her first drugs seizure – and strikes gold when she stops an SUV heading for Atlanta. And as night falls on Brownsville, a suspected courier for one of the Mexican cartels is questioned about why she has tried to smuggle $50,000 in cash out of the country.

Officers' suspicions are raised on the Pharr International Bridge when a routine X-ray reveals suspicious packages hidden inside the tyres of a pick-up truck. Convinced that they contain hardcore narcotics, Customs and Border Protection officers call in a specialised team to help extract the packages from the tyres. Meanwhile, in McAllen, officers seize a huge shipment of marijuana - worth over $50 million.

People forced out of their homes in Honduras by the notorious MS-13 gang plead their case for asylum in America. Officers discover 3,000lb of marijuana hidden in a cargo truck.

Officers prepare to transfer two members of a cartel. In Laredo, a cop from Caracas, Venezuela, pleads his case for asylum in the United States.

A refugee from Venezuela tells officers how she paid human traffickers to smuggle her to the Mexico-US border. In Laredo, an American couple are caught smuggling methamphetamine.

A family from Venezuela plead with officers to enter America. In Progreso, a suspected drug dealer is caught smuggling pills in his underpants.

More than 100 boxes full of drugs are discovered inside an unlikely vehicle at the World Trade Bridge. In Progreso, a suspected gang member attempts to cross into the United States.

A man kidnapped and beaten by a Mexican drug cartel flees across the bridge into America. At Progreso International Bridge, a woman is caught hiding anti-anxiety pills in her bra.