Arrests of Immigrant Children at Border Climb, Fueling Concern for Biden Team

Immigrant children and families are again heading north to the U.S.-Mexico border in increasing numbers after a lull, signaling the possibility of a fresh humanitarian crisis and an early challenge for the incoming Biden administration.

The flow of these migrants, who historically have come to seek asylum at the border, had slowed in the past year after the Trump administration made policy changes that cut off access to the asylum system. The coronavirus pandemic, which prompted a wave of lockdowns across Latin America, also hindered people from traveling.

But in...