Citing the need to curb the spread of the coronavirus pandemic, the Trump administration on Friday announced it would turn away certain border-crossing migrants, including those seeking refuge, by invoking sweeping powers to deny entry to foreigners whom the government determines could carry a communicable disease.

U.S. officials at both land borders are being directed to rapidly process migrants who lack the authorization to enter the country and to bounce them off U.S. soil as quickly as possible starting Saturday. Acting Homeland Security Secretary Chad Wolf said migrants would be returned to Mexico or Canada "without delay," or rapidly deported to their home countries.

Standing alongside President Trump and other top administration officials, Wolf said the stringent measures stemmed from an order by the Centers for Disease Control and Prevention, or CDC. He said it would be "all but impossible" for his officers to determine whether migrants pose a public health risk since many of them arrive at the U.S.-Mexico border without medical or travel documents.

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"The CDC Director has determined that the introduction and spread of the coronavirus in the department's Border Patrol stations and detention facilities presents a serious danger to migrants, our frontline agents and officers and the American people," Wolf told reporters at Friday's White House briefing.

CDC officials did not respond to requests for comment or provide a copy of the order that gives the Department of Homeland Security the power to implement the new measures.

In addition to the restrictions for migrants, the administration also announced on Friday it would prohibit non-essential travel at the southern border under a joint agreement with the Mexican government. Like similar measures with Canada, the move does not ban commercial traffic and will not affect U.S. citizens or permanent residents.

The administration said it has the authority to enforce the new restrictions for migrants under a public health law that allows the government to turn away foreigners if the U.S. surgeon general determines they could carry a communicable disease. "This order applies to persons coming from Mexico and Canada who are seeking to enter the country illegally and who would normally be held in congregate settings like a Customs and Border Protection (CBP) station," said Health and Human Services (HHS) Secretary Alex Azar, who oversees the CDC.

At ports of entry along the borders with Canada and Mexico, CBP officers will no longer be processing migrants who are deemed "inadmissible" into the U.S., agency officials said. Asked about those who claim fear of persecution in their home countries, CBP officials said anyone whom the agency determines can't enter the U.S. because of the CDC order will be returned to the "country of last transit," meaning Mexico or Canada.

Citing the CDC order, CBP officials said they will "suspend or reduce routine queue management procedures at the limit line" across ports of entry for any migrant who appears to lack proper travel documents.

In between these border crossings, CBP agents will be "given tools" to rapidly adjudicate cases in the field after apprehending migrants and asylum-seekers. The Border Patrol agents would then decide whether to take people into custody or "expel" them to Mexico or Canada through a port of entry, CBP officials said.

Asked whether migrants at the southern border would be sent to Mexico or deported to their native countries, Wolf said some would be repatriated in "rapid fashion," while "additional populations" would be returned to Mexican territory, with that country's permission. The main objective, Wolf said, is to limit contact between agents and migrants by reducing the amount of time border crossers spend in U.S custody.

The "vast majority" of those returned under the new measures will be Mexican and Canadians, CBP officials said. The administration is in close contact with other countries to coordinate the rapid deportation of their citizens and ensure they are not held in U.S. detention centers or Border Patrol stations, the officials added.

The Mexican government has agreed to allow the U.S. to immediately return certain Central American migrants who cross the southern border without authorization, a Mexican official told CBS News. Mexico will accept migrants returned by U.S. officials as long as they hold some Mexican documentation, like an application for refugee status, the official said. Others, like families and vulnerable populations, could be accepted as well on a "case by case" basis, the official added.

Returns will only occur at ports of entry, even for those migrants apprehended in between them, and during times when Mexican immigration authorities can receive and process them, the Mexican official said.

Processing for unaccompanied migrant children, who are afforded extra protections under U.S. law, will not change and CBP will continue to quickly transfer them to the Office of Refugee Resettlement within HHS.

Homeland Security officials did not answer whether any migrants who say they fear returning to their home countries will be referred to an interview with an asylum officer. It's also unclear if Mexican asylum-seekers will be quickly deported to Mexico since U.S. law generally prohibits officials from returning migrants to places where their "life or freedom would be threatened."

The Mexican official said the fate of asylum-seekers and how they will be processed is a matter for the U.S. to figure out. Non-Mexican migrants who seek protection in the U.S. could be returned to Mexico under the Migrant Protections Protocols agreement that has been in place for more than a year, but it's unclear how they would attend their U.S. immigration court hearings under the restrictions allowed by the CDC order.

The measures announced on Friday elicited withering criticism from human rights groups and immigrant advocates, who said border officials could be violating U.S. asylum law, as well as America's obligations under intentional refugee treaties if they moved forward with the plans.

"Even before coronavirus came along, we've seen the administration take steps to make it virtually impossible for anyone to seek asylum at the southern border," Aaron Reichlin-Melnick, a policy counsel at the American Immigration Council, told CBS News. "It comes at no surprise that we heard rumblings about turning away asylum-seekers almost immediately after this crisis began."

Over the past two years, the administration has instituted a series of policies that have severely restricted access to humanitarian protections at the southern border. They include a policy that has required more than 60,000 Latin American migrants to wait in Mexico as their asylum cases are processed, a restriction that renders most non-Mexicans ineligible for asylum and more recently, bilateral agreements that allow the U.S. to re-route asylum-seeking migrants to countries in Central America, even if they don't have any connections to those countries.

The administration has defended the policies as necessary tools to curb irregular migration and to deter "fraudulent" asylum claims. But advocates say the measures have decimated America's asylum system and eroded the country's symbolism as a beacon of safe haven for those fleeing persecution.

Reichlin-Melnick said the administration is essentially exploiting the coronavirus pandemic to fulfill its restrictive immigration agenda. Instead of turning people away, he said officials should repurpose the billions of dollars being spent on constructing border barriers to create a safer way to process migrants.

During the White House briefing, the president said the new restrictions could help address "mass uncontrolled" migration. After reaching a 13-year high in May 2019, apprehensions along the southwest border dropped for eight consecutive months, rising only slightly in February, according to government data.

"We should be especially wary of any efforts targeted at asylum-seekers during a moment of crisis," Reichlin-Melnick said.