(SAN DIEGO) — The Trump administration wants up to two years to find potentially thousands of children who were separated from their families at the border before a judge halted the practice last year, a task that it says is more laborious than previous efforts because the children are no longer in government custody.

The Justice Department said in a court filing late Friday that it will take at least a year to review about 47,000 cases of unaccompanied children taken into government custody between July 1, 2017 and June 25, 2018 — the day before U.S. District Judge Dana Sabraw halted the general practice of splitting families. The administration would begin by sifting through names for traits most likely to signal separation — for example, children under 5.