During their harrowing journey from Venezuela to the Texas border, the three Zaragoza children liked to imagine the refuge they would find when they reached the United States, a place where they would finally be free from hunger and police harassment and could simply be kids.

Instead, when they reached the border in March, they were detained — dirty with mud from the Rio Grande and shivering with cold — in frigid cinder block cells. They spent sleepless nights on cement floors, packed in with dozens of other children under the glare of white lights, with agents in green uniforms shouting orders.

The siblings were booked by officers who asked questions they didn’t understand and were told to sign documents in English they couldn’t read. Even after their release three days later, they feared the U.S. would never be the haven they had longed for.

Since early 2017, one of every three people held in a Border Patrol facility was a minor, a far bigger share than has been reported before now, according to an analysis by The Marshall Project of previously unpublished official records. Out of almost 2 million people detained by the Border Patrol from February 2017 through June 2021, more than 650,000 were under 18, the analysis showed.

More than 220,000 of those children, about one-third, were held for longer than 72 hours, the period established by federal court rulings and an anti-trafficking statute as a limit for border detention of children.

For most young migrants crossing without documents, the first stop in the U.S. is one of some 70 Border Patrol stations along the boundary line. The records reveal that detaining children and teenagers has become a major part of the Border Patrol’s everyday work. The records also show that conditions for minors have not significantly improved under President Joe Biden. While the numbers of kids in Border Patrol custody peaked in 2019 under former President Donald Trump, they rose again when Biden took office and have remained high.

Those numbers could surge to new highs when the Biden administration eventually lifts Title 42, a public health order that border authorities have used for more than two years to swiftly expel most unauthorized border crossers, including many children.

But the Border Patrol has resisted making changes to its facilities and practices to adapt to children, even while officials acknowledge that the conditions young people routinely face are often unsafe.

Read the full article about immigrant children in detention by Anna Flagg and Julia Preston at The Marshall Project.