TEXAS (Reuters) — More than 3,600 migrant children were being held in U.S. border facilities as of Thursday morning, a U.S. official told Reuters, more than four times the number in late February, a sign of a growing humanitarian and political crisis for President Joe Biden’s new administration.

The number of mostly Central American unaccompanied children arriving at the U.S.-Mexico border has risen rapidly in recent weeks, with more children stuck in border patrol stations while they await transfers to increasingly crowded federal shelters and eventual release to parents or other sponsors.

The border stations were built to house adult men for short periods and could pose a COVID-19 health risk to children and staff if they grow overcrowded. Last week, U.S. health officials lifted coronavirus-related capacity restrictions on shelters for unaccompanied minors to alleviate the housing crunch, but beds have been filling up quickly.

Biden, a Democrat who took office seven weeks ago, pledged to undo many of the restrictive policies of former President Donald Trump, a Republican. In February he began allowing unaccompanied minors arriving at the border to enter the country. They had previously been sent back to Mexico or rapidly deported under a Trump-era order known as Title 42.

Republicans have savaged Biden for rolling back Trump’s hardline policies, saying his administration has encouraged illegal immigration. At the same time, Democrats have criticized Biden for keeping some Trump policies and for reopening an emergency shelter in Texas that was used under Trump.

The arrivals resemble previous surges of unaccompanied minors and families in 2014 and 2019, according to officials and experts. The roughly 3,600 children in U.S. Customs and Border Protection (CBP) custody is up from around 800 on Feb. 22.

Acting CBP Commissioner Troy Miller declined to share the child custody figures during a press call on Wednesday, saying such a disclosure could jeopardize law enforcement operations.

The Biden administration has been talking to Central American nations about keeping migrants at home and is seeking to conduct interviews with asylum seekers in their own countries, U.S. House of Representatives Speaker Nancy Pelosi, a Democrat, told reporters at the Capitol on Thursday.

The Biden administration announced on Wednesday that it would restart a program ended by Trump that will allow certain Central American children with parents lawfully living in the United States to apply for refugee status from their home countries.

Roughly a dozen Republicans led by House Minority Leader Kevin McCarthy will travel to the U.S.-Mexico border in Texas on Monday to address what they say is a dire crisis.

McCarthy requested a meeting with Biden last week to discuss the border, but said he has not heard back from the president, whose policies he blames for the recent border surge.

“(Biden) hasn’t even acknowledged the crisis he created, let alone set a time to meet to solve it,” McCarthy said.

The Biden administration has been loath to characterize the situation on the border as a crisis, although senior officials have variously called it a challenge or “vexing problem.”

The U.S. government is still expelling the majority of migrants, including families, to Mexico under a COVID-19 health measure known as Title 42, or rapidly deporting them elsewhere.

But some non-Mexican families are being allowed into south Texas after the Mexican state of Tamaulipas stopped accepting families with small children.

Sister Norma Pimentel, executive director of Catholic Charities of the Rio Grande Valley, said during a virtual event on Thursday that between 500 and 800 family members are being released into her network of shelters each day.

Reporting by Ted Hesson and David Morgan in Washington; Additional reporting by Mica Rosenberg in New York; Editing by Ross Colvin, Matthew Lewis and Chizu Nomiyama