(CNN) — With tens of thousands of migrants massed in northern Mexico, the expiration overnight of the US Covid-era border restriction policy known as Title 42 has American border communities on edge, worried an already challenging humanitarian crisis will worsen as crossings climb.

"We're boarding up like there were a hurricane coming," Victor Treviño, the mayor of Laredo, Texas, told CNN Thursday evening.

Live updates: The latest from the border after Title 42's expiration

The South Texas counties of Cameron and Hidalgo issued disaster declarations ahead of the order's expiration at 11:59 p.m. ET Thursday to help free up state and federal resources as US troops, agents and other federal workers surged this week toward the southern border to help handle a possible crush.

Still, officials hit a roadblock late Thursday as a federal judge temporarily blocked the Biden administration from releasing screened and vetted migrants from Border Patrol without court notices — a method it had planned to use to alleviate immense strain on border facilities. The ruling sidelines a tactic used by prior administrations and is "very harmful" in light of potential overcrowding, US Homeland Security Secretary Alejandro Mayorkas told CNN on Friday.

Meantime, new rules will limit asylum claims by migrants who traverse other countries en route to the US-Mexico border and closely track migrant families released into the US during the deportation process. The asylum rule, though, quickly drew a lawsuit from the American Civil Liberties Union and others who said it echoes Trump-era policy, breaks with US and international law and puts vulnerable migrants in harm's way.

Here are the latest developments during the first chaotic hours of the new US immigration enforcement policy:

• Mayorkas said on "CNN This Morning" the border situation reflects "a fundamentally broken immigration system that hasn't been fixed for more than two decades" and the need for "Congress to provide us with the resources that we need."
• Immigration and Customs Enforcement said late Thursday it is adding 5,000 detention beds and eliminating Covid-19 tests requirements for detainees.
• The legal wrangling includes a federal lawsuit by the New York Civil Liberties Union against Orange and Rockland counties for blocking the arrival of asylum seekers from New York City. The counties issued executive orders barring hotels from making rooms available to migrants.

Over the last two days, more than 10,000 migrants daily were taken into custody, US border authorities reported, marking a record for daily encounters and continuing an upward trend in border arrests. And about 155,000 migrants were estimated to be in shelters and on streets across northern Mexican states bordering the US, a source familiar with federal estimates said this week.

In El Paso, Texas, about 1,000 migrants waited Thursday afternoon to be processed outside a border gate, US Border Patrol Chief Raul Ortiz said, beyond the 1,500 who were processed by border agents the previous two days.

Among them was a woman with a cut on her hand from barbed wire she'd just crossed along the border, she told CNN. A friend pointed to his ankle, revealing a gaping wound, and continued walking toward immigration authorities.

"The situation is tough in our countries," the man told CNN, explaining why he'd made the journey.

This isn't the first time El Paso has seen an influx at the border, and responding every few months to such swells is not sustainable, Mayor Oscar Leeser told CNN Thursday.

"We can't continue to do this for eternity," he said.

Title 42 had allowed US authorities since 2020 to swiftly expel undocumented migrants with some exceptions, ostensibly to stop the spread of Covid-19. Under it, authorities expelled migrants at the US-Mexico border more than 2.8 million times, according to US Customs and Border Protection data.

With the policy lapsing alongside the country's public health emergency, the US now is leaning instead on a decades-old protocol with new wrinkles: Title 8, which could carry heavier legal consequences for those crossing unlawfully but often takes more time than Title 42 expulsions.

Just before Title 42 expired, the US warned migrants the change does not mean the way is clear for unlawful entry: "Do not believe the lies of smugglers. The border is not open," Mayorkas said.

Border community leaders plead for help

With migrants said to be crowded at the border, leaders of US border towns continue to plead for help meeting the migrants' needs as makeshift encampments proliferate and social services are pushed to the brink.

Laredo's mayor worries for migrants' safety, noting Laredo does not have a permanent pediatric intensive care unit, he said.

"I don't want to see any child get gravely ill and not be able to treat them," Treviño said.

Yuma, Arizona, has seen daily migrant arrivals climb in the last month from 300 to 1,000 or more, Mayor Douglas Nicholls said. He wants a federal emergency declaration to provide "not just money but resources on the ground," he told reporters Thursday.

"A full response by (the Federal Emergency Management Agency) and the National Guard, like they would in any other disaster where they provide boots on the ground for housing, food, transportation, and health care — that would be the beginning," Nichols said.

The border crisis was "avoidable for a long time" — if immigration reform been put in place — Treviño said. Now, his community is paying a price.

"At the end of the day, what has always been a federal problem for decades now has become a local problem for our border communities," Treviño said.

Biden administration plans policy changes

A court ruling late Thursday took away a tool the Biden administration had intended to use to manage the number of migrants in US Customs and Border Protection custody. A federal judge in Florida temporarily blocked the administration from releasing migrants from Border Patrol custody without court notices; the administration is expected to appeal.

The administration had prepared to release some apprehended migrants without court dates and a requirement to check in with Immigration and Customs Enforcement amid immense strain on border facilities, according to the Department of Homeland Security. It has previously done so when facing a surge of migrants after they're screened and vetted by authorities.

The judge's decision came in response to an emergency motion from Florida, which has previously taken issue with the release of migrants from custody. A preliminary injunction hearing is scheduled for May 19, according to the judge's order.

Customs and Border Protection will comply with the order, it said early Friday, but called it a "harmful ruling that will result in unsafe overcrowding at CBP facilities and undercut our ability to efficiently process and remove migrants, and risks creating dangerous conditions for border patrol agents and migrants."

The expectation among US officials has been that Biden's new asylum rule may slow down crossings as migrants try to figure out what it means for them, a source familiar with the planning said. In the interim, officials — in their planning — expected parole on a case-by-case basis might become available again.

The concern, however, is that families may send their children across the border alone since unaccompanied minors are exempt from the new asylum rule. The Health and Human Services Department, which is charged with the care of migrant children, has expanded capacity in anticipation of any surge.

This would not be the first time that migrant mothers self-separate from their children in response to immigration policies that don't apply to unaccompanied children. CNN reported on mothers self-separating from their children in 2021 in response to Title 42 — which also did not apply to unaccompanied minors.

As Title 42 let border authorities swiftly turn away migrants at the US-Mexico border — often depriving them of the chance to claim asylum and dramatically cutting down on border processing time — it also carried almost no legal consequences for migrants crossing, meaning if they were pushed back, they could try to cross again and again.

Now, US officials will lean more on the decades-old Title 8, under which migrants could face more severe consequences for crossing the border unlawfully, such as being barred from entering the US for at least five years, they've said.

While Title 8 carries more legal consequences, including prosecution for those caught a second time, processing times under that authority take longer than Title 42 expulsions and could strain already pinched resources.

Title 8 allows for migrants to seek asylum, which can be a lengthy and drawn-out process that begins with what's called a credible-fear screening by asylum officers before migrants' cases wend through immigration courts.

The administration is also introducing new measures. A new regulation going into effect this week would largely ban migrants who traveled through other countries on their way to the US-Mexico border from applying for asylum in the United States — with some exceptions.

The rule, proposed earlier this year, will presume migrants are ineligible for asylum in the US if they didn't first seek refuge in a country they transited through, like Mexico, on the way to the border. Migrants who secure an appointment through the Customs and Border Protection One app will be exempt, according to officials.

The State Department plans eventually to open around 100 regional processing centers in the Western Hemisphere and "in the coming days" expects to launch an online platform for immigrants to make appointments, Homeland Security officials said.

The rule is a necessary measure to stem the flow of migration while offering other legal pathways for migrants to come to the US, Biden administration officials have said. But the ACLU in its lawsuit disagreed:

"The Biden administration's new ban places vulnerable asylum seekers in grave danger and violates US asylum laws. We've been down this road before with Trump," Katrina Eiland, managing attorney with the nonprofit's Immigrants' Rights Project, said in a statement. "The asylum bans were cruel and illegal then, and nothing has changed now."

The ACLU, along with the ACLU of Northern California, the Center for Gender and Refugee Studies and the National Immigrant Justice Center sued in the US District Court for the Northern District of California.

The Biden administration is also rolling out a new program for migrant families released in the United States to track them as they go through a speedy deportation process, including a measure that would require they stay under home confinement, sources familiar with the plans said.

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