WASHINGTON — Alejandro N. Mayorkas, the secretary of homeland security, told a House committee on Wednesday that the situation at the Mexican border was “undoubtedly difficult,” a day after warning that he expected more apprehensions along the southwestern border this year than at any time in the past two decades.
The House hearing exposed deep political divisions on immigration without shedding light on any solutions for the thousands of migrant children and teenagers stuck in jails along the border. Democrats continue to blame the cruelty of the Trump administration’s policies, even as the Biden administration struggles to find shelter space for those youths. Republicans accused the Biden administration of incentivizing migration by pledging to unwind Donald J. Trump’s restrictionist policies.
Pressed to call the situation a “crisis,” Mr. Mayorkas told Representative John Katko of New York, the top Republican on the House Homeland Security Committee: “I’m not spending any time on the language that we use. I am spending time on operational response on the situation at the border.”
Mr. Mayorkas also reaffirmed that domestic extremism “poses the most lethal and persistent terrorism-related threat to the homeland today.” The Biden administration on Wednesday delivered to Congress an intelligence report warning of the rise of militias and white supremacists.
“The Jan. 6 attack on the U.S. Capitol and on American democracy is a searing example of this threat,” said Mr. Mayorkas, who added that his agency was also tracking the shooting of eight people, mostly Asian, in Atlanta.
The Homeland Security Department announced last month that it would require that $77 million of its grants to state and local agencies be devoted to combating and preventing domestic extremism. Mr. Mayorkas also told the committee that his department would improve its process of disseminating warnings about extremism.
He also highlighted the work the Federal Emergency Management Agency has done to roll out vaccines, including the creation of more than 900 community vaccination centers.
But the hearing was dominated by the administration’s handling of the border. Mr. Mayorkas reaffirmed the administration’s use of a pandemic emergency rule to rapidly turn single adults and some families back to Mexico or their home countries. However, the Biden administration has broken from the Trump administration in welcoming unaccompanied minors. The number of those crossings has reached more than 29,700 since Oct. 1 — about 400 a day so far in March — compared with 17,100 during the same period last fiscal year.
The children and teenagers are taken by a border agent first to a detention facility, where they are then supposed to be transferred within 72 hours to a shelter managed by the Department of Health and Human Services. Those shelters were operating until recently with restricted capacity because of the coronavirus pandemic, leaving around 4,000 minors stuck in jails along the border. Some have been left to sleep on mats with foil sheets, according to lawyers who visited a facility in Texas.
Mr. Mayorkas declined to say whether he was caught off guard by the surge of migration at the border. “I don’t know that I had any particular expectation one way or the other,” he said. “I just knew what we needed to do when we confront a situation, and in fact, we are doing it.”
Representative Bennie G. Thompson, Democrat of Mississippi and the committee’s chairman, began the hearing by criticizing the Trump administration for its restrictionist border policies and crediting the Biden administration for its efforts.
“It cannot be expected to repair in a matter of weeks everything President Trump destroyed over four years,” Mr. Thompson said. He praised Mr. Mayorkas for working to expand the capacity of shelters managed by the Health and Human Services Department.
The Biden administration is planning to move teenagers to a convention center in downtown Dallas and is opening another facility at a former oil workers’ camp in Midland, Texas. Customs and Border Protection is working to open a tent facility in Arizona.
“Clearly more will have to be done to respond to the situation while upholding our values,” Mr. Thompson said. “What we must not do is return to the morally bankrupt policies of the last administration.”
The exchanges between Republicans and Mr. Mayorkas grew heated at times. Representative Clay Higgins of Louisiana called the hearing “quite nauseating” and accused the secretary of coming with “a prepared narrative.”
Republicans questioned Mr. Mayorkas’s decision to deploy FEMA to the border to help find shelter for the young migrants given the pandemic.
And they asked whether the Homeland Security Department was testing migrants released by border agents into South Texas for the virus. While the Biden administration continues to use a Trump-era pandemic emergency rule to turn away most migrants, some families have made it into Texas because of a change in Mexican law that prohibits some authorities from detaining small immigrant children.
“If they’re not tested at the Border Patrol stations as I outlined earlier, there are different capabilities upon which we are relying on the testing of individuals before they are released,” Mr. Mayorkas said, adding that the administration was working on testing everyone in the custody of Border Patrol agents.
The administration has offered to fully reimburse local governments for the cost of testing migrants, but Gov. Greg Abbott of Texas, a frequent critic of Mr. Biden’s immigration agenda, has not made such a request to FEMA. Instead, he wants the federal government to do the testing.
Felipe Romero, a spokesman for the mayor of Brownsville, Texas, said migrants released into the community by border agents had a coronavirus positivity rate of 2.3 percent, compared with 7 percent among the town’s residents.
The partisan sparring came as House Democrats prepared to introduce legislation that would create a pathway to citizenship or legal status for people brought into the country as children, for others granted temporary protected status for humanitarian reasons and for farm workers.
Mr. Mayorkas endorsed the effort. “I think they strike at some of the core needs, the core fixes that the immigration system requires to move us forward in a better way,” he said.
But the hearing showed that immigration changes remain a polarizing topic.
“I have rarely seen an issue that is more politicized and used as a political weapon than immigration,” said Representative Elissa Slotkin, Democrat of Michigan. “There is no contradiction between providing significant security for our borders and treating people humanely.”
The Republicans spent much time criticizing the Biden administration on its messaging to deter migration, even as immigration experts have said there is a lack of evidence that any official messaging is effective when smugglers are facilitating migration north.
Representative Michael McCaul, Republican of Texas, also asked why the Biden administration halted a Trump-era program that forced asylum seekers to wait in Mexico in squalid tent camps until they received a hearing date for their claim.
“Sometimes the tools of deterrence defy values and principles for which we all stand,” Mr. Mayorkas answered, “and one of those tools of deterrence that the Trump administration employed was deplorable.”