EXCLUSIVE: House Republicans are warning the Biden administration of a "grave risk" if a Trump-era public health order that allows for migrants to be swiftly returned to their home countries is ended -- something activists have urged President Biden to do.

"Simply put, you cannot separate the border crisis from the pandemic," the letter from 26 Republicans, led by Rep. Jodey Arrington, R-Texas, says. "Repealing this order would harm Americans and immigrants alike, while pushing our resources to unsustainable levels."

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In March 2020, the Trump administration implemented "Title 42" public health restrictions in response to the coronavirus pandemic. The restrictions allow for the rapid expulsion of migrants at the border for public health reasons. Administration officials said that the order allows migrants to be returned to their countries of last transit or origin -- often within minutes and without the need for detention.

The lawmakers cite statistics that more than 200,000 migrants have been expelled in just the last four months alone, even as migrant facilities remained mostly empty in the latter part of the Trump administration.

But the Biden administration has taken a number of measures to roll back Trump-era policies. Most dramatically it has sought to implement a 100-day pause on deportations -- although this has been blocked by a Texas lawsuit. It has also moved to end the Migrant Protection Protocols (MPP) -- by allowing in migrants who had been kept in Mexico under the program.

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Republicans have been sounding the alarm that this could set off a new crisis at the border, pointing to reports of full migrant facilities and border agents being forced to release migrants into the U.S. -- a policy known as "catch and release," which was ended under the prior administration.

The Biden administration has so far remained quiet on Title 42 and not indicated that it will reverse the stance, much to the anger of migrant groups and left-wing advocacy groups.

The Republican lawmakers pointed to the damage that repealing an order could do to border communities, health care workers and law enforcement at the border.

"Weakening or repealing Title 42 will put our CBP officers at risk, add additional strains to the healthcare delivery system in border communities, and incentivize more illegal immigrants to come to the U.S. at a time when we must prioritize the health and safety of Americans first," the letter says.

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The lawmakers urge Biden to "seriously consider the grave risk of allowing undocumented, untested individuals into our country."

"With all the efforts the Trump administration, and now your administration, have taken to test, prevent, and treat our nation’s citizens and slow the spread of COVID-19, repealing Title 42 would be illogical and indefensible," they said.

Republicans have been expressing intense concern at Biden’s immigration agenda, and seem likely to oppose an immigration proposal introduced last week that would grant millions of illegal immigrants a pathway to citizenship.

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Meanwhile, Biden’s nominee to lead the Justice Department, Merrick Garland, said this week he "hadn’t thought" about whether illegal border crossings should remain a crime.

"Well, I haven’t thought about that question. I just haven’t thought about that question," Garland said. "I think the president has made clear that we are a country with borders and with a concern about national security. I don’t know of a proposal to decriminalize but still make it unlawful to enter. I just don’t know the answer to that question. I hadn’t thought about it."