It's turning into the largest influx of asylum seekers on U.S. soil since the 1980 Mariel boatlift out of Cuba.
Since October, more than 52,000 children — most from Central America and many of them unaccompanied by adults — have been taken into custody. That's nearly double last year's total and 10 times the number from 2009.
President Obama has called on Congress to supply nearly $4 billion simply to deal with the problem. In the meantime, U.S. officials are doing what they can to discourage Central Americans from sending their children in the false belief they will readily be admitted to live with relatives.
As the crisis continues, here's an explainer on some of the key questions facing policymakers:
What is fueling this influx? Why have so many children from Central America attempted to enter the U.S. over the past nine months?
A study by the U.N. High Commissioner for Refugees found that 58 percent of the unaccompanied children are motivated by safety concerns, fearing conditions back home.
Their home countries have been racked by gang violence, fueled by the drug trade. According to U.S. Customs and Border Protection, "Salvadoran and Honduran children ... come from extremely violent regions where they probably perceive the risk of traveling alone to the U.S. preferable to remaining at home."
There's violence in Guatemala, too. Many Guatemalan children, however, come from poor rural areas and may be seeking economic opportunities. The same is true for children from poorer parts of El Salvador. For many, the prospect of reuniting with family members in the U.S. is also a powerful motivating force.
Central American families may have been misled by rumors — often spread by profit-seeking smugglers — that their children will readily be reunited with relatives already in the U.S.
Republicans argue that the president's 2012 decision not to deport so-called dreamers — young adults brought to the country illegally as children — has led more families to hope for similar treatment.
Why are Central American children treated differently than Mexican children attempting to cross the border illegally?
U.S. policy allows Mexican child migrants to be sent back quickly across the border. However, under a 2008 law meant to combat child trafficking, the Trafficking Victims Protection Reauthorization Act, children from Central America must be given a court hearing before they are deported (or allowed to stay). Given the huge backlog of cases, they may have to wait years for a hearing.
"Because of a backlog, which is growing greatly with the recent influx, in essence a kid released tomorrow could stay in the U.S. for up to three years waiting for that date," explains NPR's Carrie Kahn. "And for most of these kids, that's three years with a long-lost relative or three years away from extreme poverty and violence."
In the meantime, as many as 90 percent of the children stay with relatives or family friends already living in the U.S., with the rest placed in foster care, according to the Migration Policy Institute.
President Obama recently asked Congress to amend the 2008 law to make it easier to repatriate Central American children more quickly.
President Obama wants nearly $4 billion to help deal with this backlog. How will Congress respond?
The administration on Tuesday asked Congress for $3.7 billion to deal with the immigration crisis, as part of an "emergency" package of funds that would also help pay for Western wildfires. The money would be spent on additional Border Patrol manpower, detention facilities and more judges, while also improving care for children during the deportation process.
The request carefully sidesteps addressing questions of current immigration law. For that reason, debate may be limited to dealing with the immediate crisis, rather than how and whether to change policies.
The Senate Appropriations Committee will hold a hearing on the matter on Thursday. House leaders did not signal immediate approval or disapproval, but Kentucky Republican Rep. Hal Rogers, who chairs the House Appropriations Committee, told Politico, "Plainly, the situation for many of these unaccompanied children is extremely dire, and the United States has both a security and a moral obligation to help solve the crisis at hand."
What effect — if any — will all this have on the larger immigration debate?
The U.S. Conference of Catholic Bishops and other groups advocating for immigrants are calling for the children to be treated as refugees who are fleeing violent criminals in their home countries.
The U.N. High Commissioner for Refugees echoed that desire on Tuesday, noting that this is a regionwide problem.
But the migrants are unwelcome among groups traditionally concerned with illegal immigration. Most dramatically, last week protesters blocked busloads of migrant children and families from entering a processing facility in Murrieta, Calif.
"Word has gotten out around the world about President Obama's lax immigration enforcement policies, and it has encouraged more individuals to come to the United States illegally, many of whom are children from Central America," House Judiciary Committee Chairman Robert Goodlatte, a Virginia Republican, said last month.
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