Democratic National Committee chairman Tom Perez and other immigration advocates on Tuesday tried to get access inside the New Life School in Melrose, where 58 migrant children recently separated from their families are being educated.

They were told that until the federal government gives approval, they were not allowed entrance to the site.

Perez condemned the practice of separating migrant children from their families at the U.S. border in a news briefing afterward.

MORE: Vigil calls for reunification of families separated at border

There have been mixed reports over just exactly how many migrant children are staying in New York City, but more than 2,000 migrant children have been separated from their families at the border since April, in the wake of the Trump administration’s new "zero tolerance" policy. Proponents of the law say the stricter practice is needed to secure the border, but Perez calls it an illegal policy.

It's unclear how long the children will be in Melrose or where they're headed next. After President Donald Trump's executive order last week, the administration says children will be reunited with their families after their parents' deportation proceedings are done.