On Thursday, two days after its original deadline, the Trump administration announced that it has complied with the first part of a court order to return the nearly 3,000 migrant children separated from their parents in recent months.

Administration officials had been under a mandate to reunify the youngest minors, or migrants under the age of 5, with their families by Tuesday — and by Thursday morning, they say they have reunited 57 of the 103 children who fit that criteria. Officials determined that the rest, which constitute nearly half the group, are ineligible for reunification due to a variety of reasons, ranging from their parents' criminal records to the fact that some self-proclaimed parents were not their parents at all.

"Throughout the reunification process our goal has been the well-being of the children and returning them to a safe environment," said the heads of the three agencies collaborating on compliance — Health and Human Services Secretary Alex Azar, Homeland Security Secretary Kirstjen Nielsen and Attorney General Jeff Sessions.

"Of course, there remains a tremendous amount of hard work and similar obstacles facing our teams in reuniting the remaining families," the trio of department chiefs added in a joint statement. "The Trump administration does not approach this mission lightly, and we intend to continue our good faith efforts to reunify families."

The families that have already been unified have been released from detention on the condition that they attend immigration hearings and avoid criminal activity, according to Matthew Albence, a leading official with U.S. Immigration and Customs Enforcement.

It remains to be seen whether the court will agree that the administration has properly complied with its order, however. Justice Department attorneys have been under a 6 p.m. ET Thursday deadline to explain to Dana Sabraw, the U.S. district judge behind the court order, how they returned the eligible children — and why, exactly, the rest are ineligible for return under the court's guidelines.

Sabraw had said earlier this week in court that he expected the government to be able to reunite at least 63 children with their parents by the end of Tuesday.

The group that brought the lawsuit, the American Civil Liberties Union, expressed its own deep skepticism of the administration announcement.

"If in fact 57 children have been reunited because of the lawsuit, we could not be more happy for those families," Lee Gelernt, deputy director of the ACLU Immigrants' Rights Project, said in a statement Thursday. "But make no mistake about it: the government missed the deadline even for these 57 children. Accordingly, by the end of the day we will decide what remedies to recommend to the court for the non-compliance."

The dueling statements come amid continued uncertainty over the number of young children who were separated and placed in federal custody during the implementation of Trump's "zero-tolerance" immigration policy. That total stood at 101 on Friday, according to officials, but crept upward in the following days, even as the ACLU suggested that there could be still more eligible names that officials are missing.

But the principal point of contention is likely to be the matter of eligibility: How did federal officials decide that more than three dozen children cannot be safely returned to their parents at this time — and was that decision in line with the court's criteria?

Nearly half of the children still separated from their families remain so due to "safety concerns" related to the individuals identified as their parents, according to the department of health and human services. Those concerns include charges or convictions for violent crimes.

The agency says others were found to have been falsely claiming status as the kids' parents, and that about a dozen other individuals have already been deported, some of whom "chose to leave their children behind," notes Albence.

U.S. authorities are "under no obligation to bring [deported adults] back for reunification," he added. "If they want their children to return to them," working with a consul will "help facilitate that. We don't have the legal authority to bring those people back into the country. They have no lawful right to be here."

Amid the disputes over this week's deadline, another, still larger one looms in the weeks to come. In the same order addressing the youngest migrant children, Sabraw also mandated that older minors aged 5 through 17 — the rest of the nearly 3,000, in other words — must be returned to their parents by July 26.

Officials are expected on Thursday to explain how they plan to do so.

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