US officials have likely lost track of up to nearly 6,000 unaccompanied migrant children, thousands more than politicians were alerted to in May, according to a new review of federal data.
Trump administration officials last month acknowledged that nearly 1,500 unaccompanied minors reached America's southern border without their parents and were placed with sponsors who may not have stayed in touch with officials.
But according to a , those numbers were only a snapshot of a three-month period in the last financial year and the figure is much higher.
“There is a lot more,” a former Office of Refugee Resettlement field specialist, who was responsible for checking on the well-being of children placed with sponsors, said.
“You can bet that the numbers are higher. It doesn’t really give you a real picture.”
The new estimate comes amid widespread criticism of President Donald Trump's decision to separate parents and children at the US border.
Trump told Republican politicians on Tuesday he backed their efforts to craft an immigration solution that ends the politically toxic practice of separating families on the US-Mexico border.
Just hours after doubling down on his administration's much-derided policy that triggers separations of migrant children from their parents, Trump braved frustrated and in some cases angry fellow Republicans to assure he wanted their swift resolution to the crisis.
While top officials have stood by Trump's "zero tolerance" approach, insisting children are being held in humane conditions, criticism has swelled from international rights groups, Christian evangelicals, former US first ladies and the president's own Republican Party.

Border patrol agents detain migrants near the US-Mexico border. Source: Getty Images North America
Democrats who have visited minors in detention in Texas and California describe crying children held in cage-like conditions behind chain-link fencing, with no idea when they will see their parents again.
An audio recording purported to feature Central American children separated from their parents sobbing and wailing has also struck a nerve.
With emotions running high, a handful of House Democrats protested the Trump meeting, yelling out at Trump in a rare face-to-face demonstration against a president by sitting members of Congress.
"Quit separating the kids!" Juan Vargas, a Democrat from southern California, shouted as Trump exited the meeting. "Mr President, don't you have kids?"
Politicians emerged from the 45-minute huddle energised that Trump was giving his backing to legislation that House leaders expect to bring to a vote this week.

Homeland Security Secretary Kirstjen Nielsen and President Donald Trump. Source: AP / Jacquelyn Martin
It contains several of Trump's main priorities, including border wall funding, protecting young "Dreamer" immigrants who were brought to the country as children and curbs on legal immigration programs such as an end to the visa lottery.
House Republican Mario Diaz-Balart said the priority of ending the separations has been slotted into a compromise bill currently under consideration and favoured by GOP moderates.
"Not only does he support the compromise bill, but he backs it all the way," Diaz-Balart said of Trump.
But even after the meeting, it was unclear whether Trump favoured that bill over a more hardline measure supported by conservatives.
White House spokesman Raj Shah said Trump "endorsed both House immigration bills" during the meeting, adding that they "solve the border crisis and family separation issue by allowing for family detention and removal."
"I'm with you 100 percent," Trump said, according to Shah.
- Additional reporting by AFP.