Mexico stops accepting US returns of some migrant families under pandemic-era policy

Members of a migrant caravan jump on a truck on their way to the Guatemalan border as part of their journey toward the United States on January 15, 2021, in San Pedro Sula, Honduras.

(CNN)The United States has been unable to return some migrant families to Mexico under a pandemic-era border policy after a change in Mexican law concerning the detention of children, according to three Department of Homeland Security officials.

The change presents an immediate challenge to the Biden administration as it grapples with increasing numbers of people along the US-Mexico border. The US is averaging 3,000 apprehensions a day along the southern border, according to two sources -- up from the previous month.

"It's a wave that will continue to be a challenge," one DHS official said.

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Over the course of the coronavirus pandemic, the Trump administration relied on a public health law to swiftly expel migrants -- including children and asylum seekers -- apprehended at the US-Mexico border, an unprecedented shift in the way the US had previously processed migrants.

The Biden administration has already said it's not its policy to return unaccompanied migrant children.

"The policy of this administration is not to expel unaccompanied children who arrive at our borders," a White House spokesperson told CNN. "The Border Patrol will continue to transfer unaccompanied children to the HHS Office of Refugee Resettlement so they may be properly cared for in appropriate shelters, consistent with their best interest."

The latest change, first reported by The Washington Post, applies to families with children under the age of 12, according to one DHS official. Some families apprehended at the border have been released into the US.

The US is "having to find alternative pathways" for families arriving in south Texas, where the largest number of families and children arrive at the border, meaning that families who are not returned to Mexico are generally processed into the US under pre-Covid protocols, another DHS official said.

Customs and Border Protection "takes very seriously the safety and well-being of its workforce and those they encounter, and we are taking even more precautions due to COVID-19. As they always have, the number of individuals crossing the border continues to fluctuate and we continue to adapt accordingly," the agency said in a statement, adding: "For those released, CBP may work with non-government organizations who will assist them through the out-of-custody process."

The number of migrants apprehended at the US-Mexico border has been on the rise since last April, when apprehensions hovered around 16,000. In December, that climbed to around 70,000, according to Customs and Border Protection figures. The uptick has been fueled in part by deteriorating conditions in Latin America and a perceived possible relaxation of enforcement.

"There is concern about impending capacity issues," one DHS official said.

The US is in discussions with Mexico about a resolution, the official said, adding that Mexico has appeared willing to work with the US.

Customs and Border Protection is building soft-sided structures in Donna, Texas, to provide processing capacity in the Rio Grande Valley, one of the busiest regions for illegal border crossings, due to a nearby processing center being closed because of renovation.

The Health and Human Services Department, which is tasked with the care of migrant children, is also reopening a facility in Carrizo Springs, Texas, that can accommodate about 700 children and can be expanded if necessary.