U.S. border agents detained almost 100,000 migrants at the U.S.-Mexico border in February, according to 2 people familiar with preliminary figures, the highest monthly total since a major border surge in mid-2019.

The tally, which has not been previously announced, reveals the scope of an increasing migrant influx at the southwest border as U.S. President Joe Biden, a Democrat, seeks to roll back some of the restrictive policies of former President Donald Trump, a Republican. February was Biden’s first full month in office.

Last month’s total would represent the highest figures for the month of February since 2006. The sources who provided the numbers to Reuters spoke on condition of anonymity.

An growing number of children arriving at the border without a parent or legal guardian has forced U.S. officials in recent weeks to scramble for housing options and take actions to speed up their release to sponsors in the United States.

The nearly 100,000 migrants detained at the border in February represent an increase over a figure of 78,000 in January. February’s total appears to be the highest monthly number since June 2019 during a large border surge that Trump cited as justification for a broad immigration crackdown.

Official statistics for last month are likely will be released next week, said a U.S. Customs and Border Protection spokeswoman.

U.S. Border Patrol agents caught at least 4,500 migrants crossing the U.S.-Mexico border in a single day on Wednesday, according to a government tally shared with Reuters, a sign that illegal entries could continue to surge in March.

Republicans have criticized Biden for rolling back Trump’s hardline immigration policies, saying the shift will lead to more illegal immigration.

Kevin McCarthy, the top Republican in the House of Representatives, sent a letter to President Biden on Friday whereby he requested a meeting to address the issue, saying he had a “major concern” with the administration’s approach to border.

“We must acknowledge the border crisis, develop a plan, and, in no uncertain terms, strongly discourage individuals from Mexico and Central America from ever making the dangerous journey to our southern border,” McCarthy wrote in the letter.

The recidivism rate among migrants attempting to cross the border illegally increased over the past year under a Trump-era policy known as Title 42. That policy, issued on public health grounds amid the COVID-19 pandemic, allowed U.S. authorities to rapidly expel migrants caught crossing. In some cases, migrants attempt to cross the border again.

Biden exempted unaccompanied children from the policy in February.