The number of illegal immigrants who crashed America’s southwest border surged in September, pushing the 12-month total of the fiscal year to 521,090 — a 25 percent increase over the previous year — according to government data released Tuesday.

This includes people apprehended near the international boundary by U.S. Border Patrol agents, along with foreigners deemed inadmissible at border crossing stations. It does not include people who have presented themselves at border crossing stations seeking asylum.

Experts generally estimate that for every apprehension, one illegal border crosser makes it into the interior of the United States.

But a pair of senior administration officials who briefed reporters on condition of anonymity said the statistics demonstrate the loopholes that tie the hands of law enforcement officers and create a catch-and-release system that makes quick deportation impossible.

Of the 50,568 illegal immigrants caught in September, 20,120 were adults and children traveling together — what the government calls “family units.” That is the highest number in that category of any September on record.

Nearly all of them were from countries other than Mexico, a reality that, for a variety of reasons, makes it impossible for the government to send aliens back in a timely manner.

“What we’d like to convey, more than anything else, is the unique nature of the border crisis today … is that the aliens are being apprehended, but they cannot be removed,” one official said.

The numbers show that illegal immigration has returned to levels typical during Barack Obama’s presidency after a steep drop during President Donald Trump’s first year in office. The numbers also highlight an ongoing problem that goes beyond attention-grabbing stunts like the massive migrant caravan now moving North through Mexico.

The reasons for the spike in border crossings are well-known to people who follow immigration closely. They revolve around laws and court rulings that create an immigration Catch-22 that treats Mexico differently from noncontiguous countries.

If a Mexican child or family comes across the border, U.S. officials can turn them back within a matter of hours or days. Not so for those from Central American countries such as Honduras, Guatemala, and El Salvador.

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Two main loopholes. Travelers from anywhere else create challenges in two ways:

1.) The William Wilberforce Trafficking Victims Protection Reauthorization Act (TVPRA), last modified in 2008 and intended to combat child trafficking, requires U.S. authorities to remove a child traveling alone from detention after 72 hours. Officials, at taxpayer expense, place those children with sponsors in the United States. Many of those sponsors are relatives who themselves are living illegally in the United States. The unaccompanied children often fail to show up for their immigration court hearings. The administration official said that of the unaccompanied minors from Central America apprehended in fiscal year 2017, only 1.8 percent have been returned to their home countries.

2.) A 1990s court settlement and rulings by a federal judge in California with jurisdiction over it require children traveling with adults to be detained for no longer then 20 days. Administration officials tried to address that earlier this year by filing criminal charges against the parents and detaining them. But the backlash over separating them from their children prompted Trump to reverse the policy in June. The administration official said that only 1.4 percent of the Central American adults and children traveling together in fiscal year 2017 have been returned.

Trump administration officials argue that exploitation of those loopholes has led to a dramatic change in the nature of illegal immigration over the past two decades. In 2000, roughly 98 percent of illegal border crossers were adults from Mexico traveling alone. Today, about 60 percent are from Central America.

“The problem is that, once apprehended, they can’t be sent home.”

The official said that rather than trying to evade Border Patrol officers, as illegal immigrants once did, illegal immigrant families seek out Border Patrol officers because they understand how the chain of events it triggers will lead to their release into the United States.

“The problem is that, once apprehended, they can’t be sent home,” he said.

The official noted that 96 percent of “family units” apprehended are from Northern Triangle countries even though those nations are much farther away than Mexico and collectively have a much smaller population. Roughly three out of every four unaccompanied minors also are from those Central American countries.

Congress urged to act. The official posed a hypothetical situation of what would happen were the TVPRA extended to children traveling from Mexico.

“Does anybody on this call doubt for one second that we would see a drastic surge in the arrival of unaccompanied minors from Mexico?” he asked.

The official renewed the president’s call for Congress to close loopholes to allow for the long-term detention of families pursuing asylum claims or making other challenges to deportation in immigration court.

“If you could return them home, there would be no crises — period,” he said.

Ira Mehlman, a spokesman for the hard-line Federation for American Immigration Reform (FAIR), agreed.

“This was entirely predictable, especially with all the publicity they got over the summer … We’re going to see more of that,” he told LifeZette.

The administration official also decried a 1,700 percent increase in asylum claims over the past decade, which he said results in legitimate claims’ getting “buried like a needle in a haystack” of meritless petitions.

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Mehlman said no changes in the conditions of Honduras, Guatemala, or El Salvador justify that kind of a spike in asylum petitions.

“Conditions there certainly are not 1,700 times worse than they were a decade ago,” he said.

Roughly 80 percent of people make it past the initial screening that allows them to be released. But the official noted that many of those people do not even pursue their asylum claims in court. Of those who do, roughly 80 percent get denied.

The Department of Justice (DOJ) has attempted to address the problem by sending immigration judges to the border to prioritize new cases. But a second official who spoke with reporters said the cases simply take too long to resolve.

For instance, he said, the government must give illegal immigrants 10 days to consult with lawyers before proceedings can begin. Appeal deadlines run 30 days.

By the time a decision comes, the foreigners already have been released and are harder to track down to enforce deportation orders.

“We cannot get under that 20-day window,” the second official said. “It’s impossible.”