Matthew Price joins agents as they check vehicles crossing the border
Concern is growing in the US about how to stop drugs being smuggled into the country from Mexico. There are also fears that the rampant violence between Mexican drugs cartels could spread across the border.
The boundary, some 2,000 miles (3,200km) long, between Mexico and the US is reported to be the busiest international border.
Every day, hundreds of thousands cross legally but every day also sees money and weapons smuggled south, and drugs brought across to the north.
In the Texan city of El Paso and the Mexican city of Juarez, monitoring the border has become a huge problem. The two communities live right up against one another, at the heart of a drugs smuggling route that is worth billions.
If you head out with the US Border Patrol here you get a good idea of how hard it is to stop traffickers getting across.
Agent Joe Romero and his colleagues have a huge desert region to patrol.
Fences have been built in some places, but Agent Romero agrees that surveillance and fences alone cannot stop the drugs trade.
"It's a huge business. It's a major part of an economy. Whether it's a legal economy or an illegal economy it's a big part of that. And there's a big demand for it. That side is supply, and there's a big demand for it on the US side."
As long as Americans are buying, Mexican drug cartels will continue to sell.
Up the road, at the El Paso field office of the US Drug Enforcement Administration (DEA), they have been burning marijuana in a special incinerator.
Nearby, two undercover agents are packing up more than 30kg of cocaine, seized in a raid just two days earlier. It's being sent off for analysis.
In the warehouse next door, Special Agent Joseph M Arabit shows off several tons of seized drugs.
Joseph Arabit of the DEA shows how some drugs were smuggled
Plenty of narcotics though are still getting through.
The FBI estimates that between 40% and 60% of the drugs smuggled into the US come in via the Juarez-El Paso corridor. Other agencies dispute this figure, but it's a clear indication of the scale of the problem.
"I think the long-term solution is going to have to be the elimination of the cartels themselves," says FBI Special Agent David Cuthbertson.
"The Mexican government and our government, in co-operation, really need to remove the cartels at their roots, because they are multi-billion dollar criminal enterprises, who are very powerful. They are very violent and they are also very flexible."
Except for occasional random inspections, the American border authorities do not make exit inspections of people and vehicles when leaving the country. That's gotta stop
So far the US approach has been two-fold. Try and stop drugs getting in, and spend money on equipping and training the Mexican army to destroy the cartels.
The trafficking issue, however, is not a one-way street.
The Mexican government says the US authorities are failing to stop weapons and drug money from heading south across this border. Most of the weapons used by the drug cartels are easily bought in the US thanks to relaxed US gun laws.
"The Mexicans are justifiably worried and angry that weapons, very sophisticated weapons are being smuggled into Mexico from the United States and are being used by the drug cartels," says Senator Joe Lieberman, chairman of the Senate Committee on Homeland Security.
"It's been a fact of life that except for occasional random inspections, the American border authorities do not make exit inspections of people and vehicles when leaving the country. That's gotta stop."
Still, others feel it's not so simple.
"I think at the very least we need to have a national debate about the wisdom of the United States policy of prohibition," says El Paso council member Beto O'Rourke.
"The US for decades has focused on the supply side of the problem, of getting into the business of how drugs are produced in Colombia, and Peru, and now Mexico."
"It really has done nothing to limit the supply and the availability and desirability of drugs in the United States, and that's what fuelling the violence that we see in Juarez. The US drug consumer's money is what buys guns, buys the corruption of public officials, recruits new members to the cartels."
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