SAN DIEGO (AP) U.S. immigration authorities separated more than 1,500 children from their parents at the Mexico border early in the Trump administration, the American Civil Liberties Union said Thursday, bringing the total number of children separated since July 2017 to more than 5,400.

The ACLU said the administration told its attorneys that 1,556 children were separated from July 1, 2017, to June 26, 2018, when a federal judge in San Diego ordered that children in government custody be reunited with their parents.

Children from that period can difficult to find because the government had inadequate tracking systems. Volunteers working with the ACLU are searching for some of them and their parents by going door-to-door in Guatemala and Honduras.

Of those separated during the 12-month period, 207 were under 5, said attorney Lee Gelernt of the ACLU, which sued to stop family separation. Five were under a year old, 26 were a year old, 40 were 2 years old, 76 were 3, and 60 were 4.

It is shocking that 1,556 more families, including babies and toddlers, join the thousands of others already torn apart by this inhumane and illegal policy, said Gelernt. Families have suffered tremendously, and some may never recover.

The Justice Department declined to comment.

The count is a milestone in accounting for families who have been touched by Trumps widely maligned effort against illegal immigration. The government identified 2,814 separated children who were in government custody on June 26, 2018, nearly all of whom have been reunited.