LOS ANGELES — A federal judge on Thursday gave the Trump administration six months to locate thousands more children and parents who were potentially separated at the southern border under a policy intended to deter illegal immigration.
Early this year, it came to light that many more children most likely had been forcibly separated from their parents even before a border-enforcement policy known as zero tolerance was officially unveiled in the spring of 2018. Under the policy, nearly all adults who entered the country illegally faced criminal prosecution, and any children accompanying them were placed in shelters or foster care. They often ended up hundreds or thousands of miles apart for weeks or longer.
Judge Dana M. Sabraw of the United States District Court for the Southern District of California had asked the government to devise a plan to account for the additional children and their families. The request came after a report from government inspectors in January revealed that the Trump administration most likely separated thousands more children from their parents than had been previously reported, because of a lack of coordinated formal tracking among the various federal agencies involved.
“The order shows that the court continues to recognize the gravity of this situation,” said Lee Gelernt, the lead attorney in a lawsuit filed by the American Civil Liberties Union that resulted in the reunification of nearly 2,800 families that were separated last year. The A.C.L.U. had asked the judge to order the government to take responsibility for additional children and families affected by the policy.
“The court once again made clear that it was not prepared to put up with any delays, and that these families must be found,” Mr. Gelernt said.
The government initially resisted accounting for the families, saying that it would be extremely challenging to find children who have since been released from government-contracted facilities and whose whereabouts was unknown.
Early this month, the government said that it could apply a statistical analysis to about 47,000 children who were referred to the Office of Refugee Resettlement, which is responsible for the minors held in custody. It could then manually review the records of those children who appeared to have the highest probability of being among those separated from their parents.
In justifying the time-consuming process, the government said that United States Customs and Border Protection had not collected specific data on migrant family separations before April 2018.
The government did not immediately respond to a request for comment.
In his order on Thursday, Judge Sabraw said that he had approved of the government’s plan for identifying additional children. However, he disagreed with a government proposal to accomplish the task in two years, writing that it must be completed in six months, or by Oct. 25, “subject to modification upon a showing of good cause.”
Last June, the judge ordered the reunification of all children and parents who had been separated by the zero-tolerance policy. That same month, President Trump issued an executive order ending the policy, which had prompted public outrage.
The families that the government must locate entered the United States on or after July 1, 2017, the earliest known date that separations occurred — and before the judge’s original order in June 2018 to reunify them. Those families reunified thus far are those whose children were in government custody when the judge issued the order in June.
The January report from the Office of Inspector General for the Department of Health and Human Services said the lack of an effective tracking system made it possible that thousands more separated families had not been accounted for by the government. It said that even before the zero-tolerance policy was official, it had noted a “sharp increase” in the number of children separated from a parent or guardian. The total number of children who were separated was “unknown,” the report said.
Two months later, Judge Sabraw ruled that the original A.C.L.U. lawsuit should be expanded to include the additional families, because they had been subjected to the same policy that had resulted in separations under “questionable circumstances,” he said.
Family separations were central to the Trump administration’s early efforts to discourage migrant families from trying to enter the United States after traveling over land through Mexico. Arrivals of families decreased while the policy was in effect but have since surged to record levels.