A spike in coronavirus infections in Mexico and along the southern U.S. border has shelved Biden administration plans to phase out the controversial public health law used to return more than 1 million migrants to Mexico, according to U.S. officials working on border policy.

The delay points to President Biden’s deepening predicament at the border, where the migration surge he has described as seasonal is growing larger this summer while coronavirus caseloads rise. Republicans have hammered Biden’s moves to ease Trump-era restrictions as a threat to public health. But the president is also taking fire from immigrant advocates who have denounced the expulsion program known as Title 42 and challenged it in court because it prevents most asylum seekers from applying for humanitarian protection under U.S. law.

Officials said last month that the government was preparing to end the return-to-Mexico policy, without providing a timetable, though several media outlets reported Title 42 would no longer be used on families after July 31. But the explosive spread of the delta variant in recent weeks, and a huge influx of Central American families crossing into the Rio Grande Valley of South Texas, have recalibrated the Biden administration’s thinking, according to four U.S. officials who spoke on the condition of anonymity because they were not authorized to discuss internal deliberations.

The administration now fears it will be blamed for a pandemic resurgence made worse by the border influx.

“It's the hottest part of the summer and apprehensions are skyrocketing!” Brian Hastings, chief of the Border Patrol’s Rio Grande Valley sector, said in a Twitter post after agents there made more than 20,000 arrests in a single week.

More than 188,000 border crossers were taken into custody in June, the largest monthly total in 21 years. This month that figure is projected to be even higher, according to preliminary U.S. enforcement data. While most single adult migrants are returned to Mexico under Title 42, the majority of families are allowed to seek humanitarian protection under U.S. law. But the arrival of more parents and children — some testing positive for the coronavirus — has alarmed border authorities and angered communities hit hard by the pandemic.

With Rio Grande Valley Border Patrol stations and migrant shelters stretched beyond capacity, and large groups with 300 or more adults and children arriving in the dangerous heat, Biden administration officials said this week they will reinstate fast-track deportations for families, while quietly acknowledging the Title 42 policy will remain in use.

Immigrant advocacy groups excoriated Biden after the Department of Homeland Security said late Monday it will use expedited removal authority to send back “certain family groups.”  

“This announcement represents a major blow to the principle of humanitarian protection for families and children seeking humanitarian protection,” Oscar Chacón, executive director of advocacy group Alianza Americas, said in a statement. “It is truly shameful to see the richest nation on earth treating families and children running for their lives be sent back to the very conditions that made them flee.”

The administration has provided few details about how the fast-track deportations will work, but one government official and one former official with knowledge of the plans said U.S. authorities will fly families back to Central America using the Electronic Nationality Verification program, which relies on biometric data to identify migrants who lack identification or travel documents.

The Trump administration made aggressive use of the ENV program, also known as “no-doc flights.” Biden officials had not been doing so but are now planning to deport the families directly from Border Patrol custody in less than 72 hours, said one official, who spoke on the condition of anonymity because they were not authorized to publicly discuss the plans.

Veteran border officials say the expedited removal process may be affect relatively few families and could be little more than a stopgap measure to ease the strain on the Rio Grande Valley, if only temporarily.

Migrants who tell U.S. agents they fear persecution if deported — which many families do — are taken out of the fast-track lane and made eligible for an interview with a U.S. asylum officer. That generally means they will be released from border custody with a date to appear in court or a request to self-report to authorities once they arrive to their U.S. destination.

“That’s exactly what happened in 2019,” Rodolfo Karisch, retired former chief of the Rio Grande Valley sector, said in reference to the record influx of parents with children who crossed the border that year seeking asylum.

“I think the administration realizes they have to do something,” Karisch said, “but there are ways around to get around [expedited removal] based on their own policies.”

Border agents in Arizona were told this week the agency is preparing to expand Title 42 to turn back more Central American families in the Tucson sector, where several large groups have crossed in the past week, according to one agent who spoke on the condition of anonymity because they were not allowed to discuss the matter with reporters.

The administration insists the decision to use the policy is made by health authorities at the Centers for Disease Control and Prevention, rather than border agencies. Unaccompanied minors, who have also recently arrived in greater numbers, have been exempted from Title 42 returns by the Biden administration.

The American Civil Liberties Union has sued the government to stop the expulsion of families under Title 42, but in recent months attorneys have negotiated with the Biden administration to scale back its use and coordinate a safe entry for vulnerable families waiting in dangerous Mexican border cities.

ACLU attorney Lee Gelernt, who has led the court challenge, threatened to put new legal pressure on the administration if the health-related expulsions do not cease. “If CDC is going to continue with Title 42, they need to be prepared for a lawsuit and to answer very specific questions in a deposition about whether they genuinely believed there was no way to process asylum seekers safely,” he said in an interview.

“The U.S. cannot close down the asylum process whenever there is any risk of a variant,” Gelernt said. “The government has more than enough resources to do it safely.”

Biden administration officials blame the Title 42 policy for an increase in repeat border-crossing attempts by migrants who try to sneak past agents again and again. The quantity of border crossers is now so large that if Title 42 were lifted, agents would not be able to safely detain migrants, especially if large numbers seek asylum, analysts say. But the policy doesn’t discourage unlawful entries either, said Andrew Selee, president of the nonpartisan Migration Policy Institute in Washington.

“Title 42 has clearly outlived its usefulness as a deterrent, and it has huge problems from a humanitarian protection standpoint,” Selee said. “But until the administration can figure out its next steps on the asylum system and how to safely keep people in a congregant setting in the middle of a pandemic, it’s hard to figure out at what moment they let go.”

The growing volume of border apprehensions and releases has once more aggravated local officials in the Rio Grande Valley and Laredo, Tex., whose communities have been slammed by the pandemic. A rising number of pediatric coronavirus cases and hospitalizations has startled health officials.

“We've never had more than five kids in the hospital; now we have 15,” Hidalgo County health official Ivan Melendez said. “With school coming up, we know it could be a disaster.”

Shelters are running out of beds, with thousands of migrants arriving each day and many testing positive for the coronavirus. The shelters have been renting hotels to isolate families who test positive. While most don't leave the hotels, there is no legal mandate that compels them to stay in place, officials said.

This week, after a visibly ill migrant mother with children who were sneezing and coughing walked into a fast-food restaurant to eat in La Joya, Tex., local residents called the police, suspecting the unmasked family was infected and staying at a nearby hotel, said Sgt. Manuel Casas.

“This is day after day,” Casas said. “We get hundreds of people, and they could all be sick.”

Hidalgo County Judge Richard Cortez asked the federal government to suspend releasing migrants who test positive for the virus to prevent its spread in his community. It was a stark departure for a county that has accommodated the large numbers of migrant families, resisting tougher border enforcement measures called for by Texas Gov. Greg Abbott (R).

On Wednesday — a day that state health officials reported more than 10,000 new cases for the first time since February — Abbott ordered state police to stop any vehicle suspected to be carrying migrants “who pose a risk of carrying COVID-19 into Texas communities.”

“The facts have changed,” Cortez said. “The volume has gotten to the point where it's not manageable.”

Arelis R. Hernández in San Antonio contributed to this report.