The number of migrants encountered at the U.S.-Mexico border in March was the most in at least 15 years, as agents for U.S. Customs and Border Protection apprehended nearly 172,000 people, according to Biden administration officials.

This included nearly 19,000 children and teenagers traveling without a parent — double the levels from February and the most ever in a single month.

The overall surge in March — a 71% spike over February's figures — illustrates the scope of the ongoing challenge President Biden faces as he seeks to enforce the border while overhauling the nation's asylum rules.

Administration officials said CPB turns adult migrants back 60% of the time because of Title 42, the health order implemented by the Trump administration aimed at limiting the spread of the coronavirus. And nearly 30% of the migrants had been previously turned back because of Title 42.

"The levels of flows pose a challenge to Border Patrol, but the high level of recidivism means that we can't look at those flows as individual people. It's often the same people coming back through," an official told reporters.

The administration has been struggling to handle the influx of children, who are not being turned away at the border. Facilities run by CBP are not designed to house children and teens. In March, there was progress, officials said. By the end of the month, an average of 507 children a day were being transferred out of CBP facilities, up from 276 per day a month earlier.

"We are moving in the right direction, but we know we know we have a lot of work ahead," the official said, noting the administration has increased the number of emergency shelter beds.

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