Homeland Security Secretary Alejandro Mayorkas announced Monday that four families will be brought to the United States to reunite with the children separated from them at the border during the previous administration, NPR reports.

While the number of reunions is small, it marks a significant achievement for the administration, which had more than 500 children still in federal guardianship after they were separated from their families at the border as part of a harsh Trump policy that’s been widely decried by human rights and legal activists.

“They are children who were three years old at the time of separation. They are teenagers who have had to live without their parents during their most formative years,” Mayorkas said. “They are mothers who fled extremely dangerous situations in their home countries, who remained in dangerous environments in Mexico, holding out hope to reunite with their children.”

Some of the children were separated from the families were taken as far back as 2017.  As many as 5,000 families were separated at the border before the courts put an end to Donald Trump’s family separation policy, which put the children into the custody of ICE agents while deporting their parents or guardians back to their home country.

At the start of the Biden Administration, as many as 550 children were still in ICE custody, living in detention facilities or hotels.  The Biden Administration set up a task force to locate and reconnect children with their parents, making a priority locating and informing their parents of their children’s location.