Washington | Thousands of migrant children are backed up in US detention facilities along the border with Mexico, part of a surge of immigration from Central Americans fleeing poverty and violence that could overwhelm US President Joe Biden’s attempt to create a more humane approach to those seeking entry into the country.

The number of migrant children in custody along the border has tripled in the past two weeks to more than 3250, according to federal immigration agency documents obtained by The New York Times, and many of them are being held in jail-like facilities for longer than the three days allowed by law.