LOS ANGELES – Federal officials said early Thursday they had reunited 57 of 103 young migrant children separated from their parents at the U.S.-Mexico border largely as part of the Trump administration's zero tolerance policy on suspected illegal crossings, but they have not returned an additional 46 for reasons including deportation and criminal histories of some of the adults.

The government began its first major wave of reuniting migrant children with their parents on Tuesday, the deadline set by U.S. District Judge Dana Sabraw for those children younger than 5. Sabraw ordered the reunifications after a class-action lawsuit filed by the American Civil Liberties Union.

Of 103 children younger than 5 who were covered by the court case, 57 had been reunited as of 7 a.m., officials said. Forty-six were "acknowledged by the court to be ineligible for reunification or determined by HHS, DHS and DOJ to be ineligible under court-approved criteria."

Sabraw's court in San Diego had ordered the government to take a streamlined approach to matching and vetting parents for reunification. Under the new guidelines, DNA testing can be used only if the government has a specific concern about a child's parentage, or if it would speed up the reunification process. But if parentage can be proved through other official means, Sabraw said, that was enough.

The judge also threw out policies that called for background checks of other adults in the household, a care plan to be established and home visits – unless officials have specific concerns they can explain and justify. Criminal background checks will still be run on the parents.