An internal Department of Homeland Security document leaked to Axios shows that 823 unaccompanied migrant children have been held in border patrol custody for over 10 days — more than a fourfold increase over the past week.

Why this matters: These facilities aren't meant to house kids for more than three days, but the recent surge of children at the southern border has overwhelmed the Biden administration's capacity to handle them.

Details: The maximum amount of time a child is legally supposed to be held in border patrol custody is 72 hours. But as of Saturday, 3,314 unaccompanied children had been in custody longer, with 2,226 for more than five days and 823 for more than 10 days.

• The document, with figures updated through Saturday, shows how the Biden administration is struggling to manage the volume of child migrants.
• The trend is accelerating. On last Monday, only 185 migrant children were being held in border patrol custody for more than 10 days.

The big picture: President Biden is telling migrants not to try to cross the border but Biden has chosen not to use an emergency order to turn away kids at the border, as was done under the Trump administration. The surge shows no sign of abating.

• Analysts cite the policy change and Biden's more welcoming rhetoric to immigrants among various factors driving the surge — along with damaging hurricanes in Central America and general desperation that intensified during a pandemic.
• Under U.S. law, U.S. Customs and Border Protection must initially receive unaccompanied children until the Department of Health and Human Services indicates there is space to accept them in one of their shelters.

After a recent visit to the border, Democratic Sen. Chris Murphy tweeted: "Just left the border processing facility. 100s of kids packed into big open rooms. In a corner, I fought back tears as a 13 yr old girl sobbbed [sic] uncontrollably explaining thru a translator how terrified she was, having been separated from her grandmother and without her parents."

• "For clarification," Murphy added in a follow-up tweet, "kids are no longer separated from their parents at the border (in this case, the girl's parents are in the US). But even though kids can now stay and apply for asylum, if they are traveling w relatives who aren't parents, the relative can't stay."
• The administration has been hurriedly securing additional facilities, including hotel rooms and temporary sites, to house the growing numbers of migrant children and families.

What they're saying: A Biden administration official tells Axios that the administration has been clear at all levels that CBP facilities are no place for children and that officials are working around the clock to transfer children to HHS shelters or the homes of vetted relatives or sponsors.