Smuggling networks that bring migrants to the United States from Central America have only grown more sophisticated and profitable under the Trump administration's harsh border policies, experts say.

The Trump administration has imposed policies to keep migrants waiting in Mexico as long as possible — but that has only created a bottleneck of thousands of migrants in Mexican border cities, in conditions ripe for violence and exploitation.

Smugglers have raised their prices in recent months, and gangs and cartels charge exorbitant fees to pass through territories they control.

Meanwhile, conditions in Northern Triangle countries continue to languish, prompting more people to flee north to escape poverty and violence.

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More than 100,000 migrants were taken into custody at the US-Mexico border last month alone.

That's the highest in more than a decade, and the seemingly neverending flow of migrant families coming to the US has sparked a frenzy within the presidential administration that had vowed to eliminate illegal immigration.

But as that number has soared in the last year, it has exposed an increasingly sophisticated and lucrative business smuggling migrants from Central America to the United States, and revealed gaping flaws in the Trump administration's insistence on deterring immigration at all costs.

These increasingly restrictive policies have resoundingly failed to deter migrants from making the long and dangerous journey to the US, experts told INSIDER.

Instead, they have created an opening for elaborate smuggling networks and criminal enterprises to exploit those who are desperate to flee violence and poverty in the Northern Triangle countries of Guatemala, Honduras, and El Salvador.

The Trump administration has attempted to stem the flow of constant border-crossings by imposing policies to limit the number of migrants who apply for asylum at ports of entry, and to force those who do apply for asylum to wait in Mexico while their cases are resolved in US courts.

Read more: The number of migrants apprehended at the US-Mexico border just keeps going up

But together, those practices have created a bottleneck of thousands of migrants waiting indefinitely in Mexican border cities, creating what experts say are perfect conditions for violence and exploitation.

"Families are coming, legitimate families, but that puts children at under a very big risk of being exploited sexually, of being drowned in the river," Guadalupe Correa-Cabrera, an immigration and border-security expert at George Mason University, told INSIDER. "Some of them apply for asylum at the regular ports of entry, but not all of them, because the time they have to wait in these ports of entry is too big. So some of them are hiring the services of smugglers to get through other ways, to get smuggled through other parts."

The Associated Press on Thursday revealed that at least 13,000 migrants across the US-Mexico border are on waiting lists just to enter the US and request asylum, leaving migrant shelters in Mexico overwhelmed and leaving migrants exposed to everything from shakedowns and bribery, to gang-related kidnappings and gunfights.

A migrant looks on with his children as they wait to hear if their number is called to apply for asylum in the US, at the border on Jan. 25, 2019, in Tijuana, Mexico. AP Photo/Gregory Bull

Karla McKanders, a law professor and Immigration Practice Clinic director at Vanderbilt University, told INSIDER that many of the migrants forced to wait in these border cities or refugee camps fear that the gangs they had fled in Central America will track them down while they wait to enter the US.

McKanders visited some of the shelters last December and met migrants who have waited months on end for the chance to request asylum on US soil, many of whom endured crimes like robbery, sexual assault, or trafficking on their journeys north.

"I think it's exacerbating dangerous conditions and putting migrants who are already vulnerable in positions that are more problematic," she said. "It's not considering that most of the individuals are fleeing from some type of persecution or dangerous conditions and it's not in line with our law or our obligations under the refugee convention that we signed."

'When you have greater black markets, migrants become more invisible'

While the cost varies and exact numbers are hard to pin down, smugglers have been charging migrant families with children thousands of dollars for the journey to the US border — often between $5,000 and $7,000. Individual adults, however, have reportedly seen charges as high as $15,000 per person, ProPublica reported.

President Donald Trump has long excoriated smugglers, once calling them "the worst scum in the world."

"Smugglers use migrant children as human pawns to exploit our laws and gain access to our country," he said in his State of the Union speech in February.

But the mixed bag of ruthless enforcement on the US side of the border and chaos on the Mexican side has helped create a thriving black market that smugglers have capitalized on, Correa-Cabrera said.

The days of lone "coyotes" guiding individuals or small groups of migrants to the border are largely over. Instead, they have been replaced with vast smuggling networks that have entrenched themselves deeply within a complex ecosystem of corrupt authorities and various drug cartels that control certain territories along popular routes to the US.

500 Central American migrants entered the United States illegally under the international bridge between Ciudad Juarez, Mexico and El Paso, Texas on May 9, 2019. NurPhoto/David Peinado via Getty Images

"Hand in hand with the strengthening of border enforcement comes sophistication and greater development, more organization of smuggling networks," Correa-Cabrera said. "This is only going to become worse."

Though the journey from Central America to the US has always been dangerous, Correa-Cabrera said the violence and criminal activity the migrants are exposed to has increased as the US government has introduced increasingly stringent policies to deter migrants from traveling to the US — or at least keep them in Mexico for as long as possible.

In short, Correa-Cabrera said the Trump administration is making matters worse.

Smugglers have raised their prices, gangs and cartels charge exorbitant fees to pass through territories they control, and those who can't pay are sometimes kidnapped or even recruited into criminal organizations to pay off their debts.

"Individual smugglers, the so-called coyotes, cannot operate independently now — they have to organize. They have to pair with criminal organizations that operate in different parts of the route, drug cartels in the northern part of Mexico," she said. "When you have greater black markets, migrants become more invisible, and they are extorted by everybody."

A US Customs and Border Protection officer reacts near an enclosure where Central American migrants are being held after crossing the border between Mexico and the United States illegally and turning themselves in to request asylum, in El Paso, Texas on March 27, 2019. Reuters/Jose Luis Gonzalez

'Once they make it into the States, they are going to change their lives'

US officials have been warning with increasing urgency against the extensive smuggling operations taking place throughout the Northern Triangle and Mexico.

In an April 16 report, officials from the Department of Homeland Security's advisory council wrote that sophisticated smuggling networks are taking advantage of the weak points along the US-Mexico border, ferrying migrants to remote areas in a scheme "designed to overwhelm existing [Border Patrol] infrastructure, and extorting migrants along the way."

Such tactics, the report's authors wrote, have meant that a large portion of the families and children who enter the US cross at "dangerous and terrifying crossings" either in remote desert areas, or on rivers using flimsy rafts.

Notably, a seven-year-old migrant girl died in Border Patrol custody last December, after she and her father were apprehended in a remote stretch of the New Mexico desert. One of the factors that delayed her medical care was the lengthy bus ride to the nearest Border Patrol station.

"These children increasingly require significant personal and medical care that exceeds the ability and capacity of CBP," the report said.

Read more: 'We've seen this coming': Why migrant children are dying in Border Patrol custody

Central American migrants are detained by US Customs and Border Patrol agents at the border wall in Ciudad Juarez, Chihuahua state, Mexico, on May 7, 2019. AFP/Herika Martinez via Getty Images

The Trump administration often frets about the "push and pull factors" that prompt migrants to flee their home countries and draw them to the United States.

While migrants are pushed to leave their home countries because of poverty and violence, Trump officials also argue that they're pulled to the US in part because of the matrix of laws that protect children from swift deportation and allow adults to go free while they wait for their asylum hearings.

That assessment is largely correct, Correa-Cabrera said.

"We have to understand that these people are doing that because they are observing that they can make it, and that somebody is going to provide them a safe route," Correa-Cabrera told INSIDER. "The poverty, the misery, the violence that they leave, the gangs affect them, but they also understand that somebody's going to provide them with a job here, and once they make it into the States, they are going to change their lives."

The government would do better to address economic insecurity in countries like Guatemala, Honduras, and El Salvador, and accept that there's a "shared responsibility" among the US, Mexico, and Central American countries to address the root causes of skyrocketing migration to the US, Correa-Cabrera said.

"We have to push for better economic conditions in the home countries — development in the Northern Triangle," she said. "Of course every country decides who can enter legally. But a country closing the border and building a wall creates a lot of problems for the whole region."