During President Joe Biden's first formal press conference since taking office, he pointed to the Trump administration as a benchmark for unaccompanied children.  

"28 percent increase in children to the border in my administration," Biden said. "31 percent in the last year, in 2019, before the pandemic in the Trump administration. It happens every single, solitary year."

Experts say the winter climate and the coronavirus pandemic both played a role in the increase this year. 

"It's the time that they travel with the least likelihood of dying on the way because of the heat in the desert," Biden said. 

READ ALSO: Biden vows action on migrants as he defends border policy  

Last year, the Trump administration turned away travelers by flexing authority provided by Title 42, a law that allows the U.S. to prohibit people into the U.S. who pose a potential health risk. 

"The other thing that we can't ignore is that last year we saw lower numbers because of the pandemic," President and CEO of Children at Risk Dr. Bob Sanborn said.

Director of Policy at the Young Center for Immigrant Children's Rights Jennifer Nagda said nearly 50,000 children were turned away due to claims that they presented "some sort of unique public health threat." 

READ ALSO: Judge orders US to stop expelling children who cross border

The practice of turning away unaccompanied children was halted by a federal judge last November.

As a result, between the months of November and February, the number of children in the care of the U.S. more than doubled, according to the Department of Health and Human Services (HHS). In November 2020, there were 1,929 children in HHS care, compared to 4,020 in February 2021. 

Editor's note: The headline of this story has been updated to more accurately reflect the content in this article.