TUCSON — Acting Homeland Security Secretary Kevin McAleenan announced on Monday the end of the practice his department refers to as "catch and release," with changes coming as early as next week.

The term refers to the process in which the federal government must release migrant families, mostly from Central America, apprehended at the U.S.-Mexico border into the interior of the United States to begin the process of seeking asylum. That process can take years, given the massive backlogs in the country's immigration courts.

McAleenan made the announcement during prepared remarks before the Council on Foreign Relations in Washington, D.C.

"(The Department of Homeland Security) will no longer be releasing family units from Border Patrol Stations into the interior," McAleenan said. "This means that for family units, the largest demographic by volume arriving at the border this year, the court-mandated practice of 'catch and release' due to the inability of DHS to complete immigration proceedings with families detained together in custody--will have been mitigated."

In doing so, McAleenan would be fulfilling President Donald Trump's campaign promise to end so-called "catch and release." It follows several steps the Trump administration has taken in recent months to restrict the ability of migrants to claim asylum in the U.S.

In a follow-up statement, the Homeland Security Department said the move is part of its "strategy to mitigate the loopholes that act as a 'pull factor' for family units seeking to cross illegally at the Southwest border."

The department said that if migrant families do not claim a fear of return, they will be "quickly" deported back to their countries of origin. But if they do express a fear of return, the families would be sent back to Mexico to await the outcome of their asylum proceedings under the policy known as the "Migrant Protection Protocols."

McAleenan noted there will be some humanitarian and medical exceptions.

There are many questions about how the program will work.

The announcement on Monday focused largely on Central American families processed by the U.S. Border Patrol. They've made up the bulk of border apprehensions this year.

To date, agents have processed nearly 458,000 migrants traveling as families this year, nearly all of them hailing from three Central American countries: Guatemala, Honduras and El Salvador.

But McAleenan did not say whether this change also will apply to the thousands of families who have spent months waiting at legal ports of entry along the U.S.-Mexico border to present their claims with Customs and Border Protection officials at the ports.

A report earlier this year from researchers at the University of California-San Diego estimated the number of migrants waiting in Mexican border cities at nearly 19,000.

Earlier this month, the Supreme Court allowed the Trump administration to implement restrictions at the border that would allow them to reject migrants who haven't first applied for asylum at another country they've traveled through.

The thousands of families waiting to seek asylum at the border also include a surging number of Mexican migrants who are fleeing cartel violence in their home states. McAleenan's announcement didn't address that population of migrants either.

While the Homeland Security Department has expanded the Migrant Protection Protocols to five border cities and has sent back about 47,000 migrants, the program is not in place at many parts of the border, including at any of Arizona's border crossings.

It's unclear if the program will expand to these areas before families apprehended there are no longer released into the U.S.

The Homeland Security Department has not responded to a request for comment.

In his remarks, McAleenan said policies such as the Migrant Protection Protocols and the new restrictions on asylum are having their intended effect. The number of migrants apprehended at the border has decreased after peaking in May.

Still, he stopped short of claiming success.

"We can’t let our progress cloud our vision," McAleenan said. "We are still at crisis levels in illegal crossings at the Southwest Border and, until we change the fundamental laws governing our immigration system, we won’t solve the underlying problem."

Have any news tips or story ideas about the U.S.-Mexico border? Reach the reporter at rafael.carranza@arizonarepublic.com, or follow him on Twitter at @RafaelCarranza.

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