WASHINGTON - The parents of 545 migrant children separated at the border by the Trump administration still have not been found, court documents show, reports the New York Times.

A wide-ranging campaign is underway to track down parents separated from their children at the U.S. border beginning in 2017 under the Trump administration’s most controversial immigration policy.

About 60 of the children were under the age of 5 when they were separated, according to court documents filed this week in a case challenging the practice.

Though attempts to find the separated parents have been going on for years, the number of parents who have been deemed “unreachable” is much larger than was previously known.

Under court order, the government first provided an accounting of separated families in June of 2018, reporting that about 2,700 children had been taken from their parents after crossing into the United States. After months of searching by a court-appointed steering committee, which includes a private law firm and several immigrant advocacy organizations, all of those families were eventually tracked down and offered the opportunity to be reunited.

But in January 2019, a report by the Health and Human Services Department's Office of the Inspector General confirmed that many more children had been separated, including under a previously undisclosed pilot program conducted in El Paso between June and November 2017, before the administration’s widely publicized “zero tolerance” policy officially went into effect.

In June 2019, under court order, the government eventually acknowledged that an additional 1,556 children had been separated from their families; 200 of them were under 5 years of age at the time they were taken into custody.

The American Civil Liberties Union, which is leading the court challenge to the family separation policy, said it had also been unable to find 362 of the children, many of whom are likely living in the United States, whose parents were deemed unreachable.