The Biden administration said on Friday that it has expanded the Trump-era "Remain in Mexico" program, which it had initially abolished before being blocked by a court order, to the Rio Grande Valley sector -- typically the busiest part of the border for illegal migration.

A DHS spokesperson confirmed to Fox that enrollments in the program, officially called the Migrant Protection Protocols (MPP), began on Jan. 19 in the sector, with migrants being returned to Mexico via the Brownsville port of entry. Migrants are also being returned from San Diego and El Paso. CBS News first reported the expansion into RGV.

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The Remain-in-Mexico policy was set up in 2019 as part of the Trump administration’s efforts to end "catch-and-release" by which migrants were released into the interior as their asylum claims were processed. 

MPP saw migrants returned to Mexico for their proceedings, and it was hailed by Trump officials as a way to remove a key pull factor for migrants coming north. Critics described the policy as cruel, arguing that it resulted in migrants camped out at the border, and put at risk of violence and exploitation by gangs.

The Biden administration began unraveling the program earlier this year and officially ended it in June. But a federal court order ordered it to be reinstated after Texas and Missouri sued, claiming that the administration had not conducted a required analysis of the policy before scrapping it. The Supreme Court upheld that order.

The DHS spokesperson noted that DHS "has repeatedly sought to terminate MPP." 

"DHS currently is, however, under a court order to reimplement MPP in good faith.  DHS continues to fight in the courts, including in a pending challenge before the Supreme Court.  In the interim, DHS is committed to abiding by the court-mandated reimplementation of MPP in the most humane way possible," the spokesperson said.

As part of the expansion, migrants returned via Brownsville will be allowed to reside in Monterrey while their hearings take place. The State Department is working with the Mexican government to secure transportation, shelter and testing for COVID-19, the spokesperson said.

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As the legal battle over MPP continues, DHS Secretary Alejandro Mayorkas issued a memo at the end of October, saying he had conducted an analysis on whether the program should be kept, modified, or abandoned -- as well as claims that the court said were not sufficiently addressed, like the program’s effect on border crossings.

He said in the memo that he has determined that MPP "should be terminated," even as he accepted that it reduced border crossings

"In reaching this conclusion, I recognize that MPP likely contributed to reduced migratory flows. But it did so by imposing substantial and unjustifiable human costs on the individuals who were exposed to harm while waiting in Mexico," he said.

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He said that the benefits of the program "are far outweighed by the costs of continuing to use the program on a programmatic basis, in whatever form"

He concluded the memo by saying that DHS would continue complying with the court injunction to reimplement MPP, but that the termination of the program will be implemented "as soon as practicable after a final judicial decision to vacate the [court] injunction."