The number of immigrants arrested or turned away at the southern border has continued to climb to levels not seen for years, according to new Department of Homeland Security data obtained by Axios.

Why it matters: The surge has been driven by an influx of migrant families and unaccompanied children, according to a DHS official. "At the moment, we have the closest thing to an open border that we've had," said Leon Fresco, an immigration attorney and member of a Homeland Security advisory committee formed by DHS Secretary Kirstjen Nielsen several months ago.

Detention centers are overcrowded, and immigration officials often aren't able to deport immigrants as quickly through expedited removal procedures.

and immigration officials often aren't able to deport immigrants as quickly through expedited removal procedures. Immigration and Customs Enforcement and Customs and Border Protection have even begun releasing migrant families into the U.S. almost immediately instead of holding them in detention, Mark Morgan, former chief of Customs and Border Protection under President Obama, told Axios. He said this could create an additional incentive for migrants.

"Unless Congress does something, we are where we are on this. There are no levers left to pull."

— Leon Fresco

The big picture: The latest data comes at a time when the Trump administration is trying to make the case that there is a true emergency at the border, in the face of skepticism in Congress and pushback over his national emergency intended to fund a border wall.

It also comes during reports of Mexican smugglers using buses for quicker, safer transportation for Guatemalan migrants. Central Americans continue to gather in large groups for the long voyage to the border.

of Mexican smugglers using buses for quicker, safer transportation for Guatemalan migrants. Central Americans continue to gather in large groups for the long voyage to the border. The Trump administration is expanding a policy that forces some asylum-seekers to stay in Mexico until their cases are completed. And President Trump has vetoed Congress' efforts to end his declared national emergency.

Between the lines: Families and children who have fled dire circumstances in their home nations are coming to the U.S. for asylum. But there are real logistical issues at the border and in U.S. immigration policy. Immigration is already a complex issue, but it has become an increasingly political one as well.

"We're infusing politics, which is making it even further a dysfunctional immigration system," Morgan said.

which is making it even further a dysfunctional immigration system," Morgan said. Another reason to be concerned about the numbers: The government's track record for caring for migrant children isn't great.

By the numbers: Historically, the number of border crossers begins escalating around March due to the warmer weather, and it typically doesn't peak until May. The U.S. has had this much border activity in the past, but could reach as many as 1 million apprehensions and inadmissibles this year, according to Morgan — levels not seen for at least a decade.

In May 2014 — the peak of the child migrant crisis under Obama— there were almost 69,000 migrants arrested or turned away. In just three weeks of March, there have already been almost 66,000 apprehensions and inadmissibles.

the peak of the child migrant crisis under Obama— there were almost 69,000 migrants arrested or turned away. In just three weeks of March, there have already been almost 66,000 apprehensions and inadmissibles. One big change: Back when reaching 1 million border enforcement actions in a year was common, the vast majority of migrants were single, Mexican adults who often made multiple attempts to cross the border. Now, DHS is dealing with the complexity of caring for tens of thousands of Central American parents and children. Laws that enabled the quick deportation of single, Mexican adults do not apply.

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