The U.S. government must identify how many families it separated before it instituted a zero tolerance immigration policy last April, according to an order issued by U.S. District Judge Dana Sabraw on Thursday.

The deadline comes three months after an internal watchdog report found that the Trump administration could have separated thousands more children from their parents even before its highly publicized separation policy took effect.

In February, the Office of Refugee Resettlement said it was too much of a “burden” to find the members of these families. Earlier this month, ORR officials said it could take up to two years to track down the potentially thousands of immigrant children it had separated from their mothers and fathers, given the fact that officials did not methodically keep track of family separations prior to April of last year.

The American Civil Liberties Union, which is part of an ongoing lawsuit against Immigration and Customs Enforcement, said the government’s quoted time frame was unacceptable. Cmdr. Jonathan White, the Department of Health and Human Services’ operational lead for the identification process, said in a report Thursday that the department could likely identify family members within a six-month window and explained that its previous one- to two-year estimate was a worst-case scenario.

“The court order is exactly what we wanted,” said Lee Gelernt, the lead lawyer in the ACLU case. “Every day a parent and child are separated is devastating.”

White said during Thursday’s hearing that he’s hopeful Health and Human Services has devised a system that can comb through the records of 47,000 immigrant children who were taken into government custody between July 1, 2017, and June 25, 2018 ― the day before Sabraw issued an injunction to halt family separations.

“It is my belief that the six month time frame is sufficient to complete this,” White said at Thursday’s hearing. “That is my operational target, but I’ve been wrong before.”