The Trump administration says it has reunited more than 1,800 migrant children with family members by a court-ordered deadline.
This includes 1,442 children brought back to their parents in US immigration custody and 378 others who were released, says a court filing.
But more than 700 children are not “eligible” to be reunited, including 431 with parents no longer in the US.
US officials took more than 2,500 children away from undocumented adults.
The separations happened under the US government’s crackdown on illegal immigration at the border with Mexico.
Of the 711 deemed ineligible, 120 children’s parents “waived reunification”, the government said on Thursday evening.
Dozens more remain separated because of “adult red flag”, referring to situations in which the child might be at risk.
San Diego federal judge Dana Sabraw ruled last month that all the detained minors separated under the policy be brought back to their families by 26 July.
US President Donald Trump halted the “zero tolerance” tactics in late June after pictures of locked-up children and audio of them crying in distress triggered uproar.
Under the practice, the children were sent to various care facilities across the country while the adults were held in detention centres or prisons.
Many of the families had entered the US illegally, while others claimed asylum at border crossings, citing violence in their home countries of El Salvador, Guatemala and Honduras.
The American Civil Liberties Union (ACLU) has said it will try to trace the hundreds of parents no longer in the US.
It said in a statement on Thursday: “We’re thrilled for the families who are finally reunited, but many more remain separated.
“The Trump administration is trying to sweep them under the rug by unilaterally picking and choosing who is eligible for reunification.”
The Trump administration earlier this month reunited more than 100 migrant children under five years old with their parents, though it missed a court-ordered deadline to do so.
It said 57 of these youngsters were back with their families, though 46 others were deemed ineligible because of safety concerns, parental deportations, or other issues.
The process has proved chaotic, with some children transported to see their parents only to end up back in their shelters after discovering their loved ones were not at the location.
US child migrants: Trump administration says 1,800 reunited