Nearly 3,000 immigrant children who may have been separated from their parents at the U.S. border remain in government custody, including roughly 100 kids who are under the age of 5, Health and Human Services Secretary Alex Azar said Thursday.

That higher figure was announced after Azar told Congress last week that 2,047 immigrant children were in the government’s care as a result of family separations under the Trump administration’s heavily criticized “zero-tolerance” policy.

In a call with reporters on Thursday, Azar said the “under 3,000” figure was determined after a recent ruling by U.S. District Court Judge Dana Sabraw that ordered the reunification of all children under the age of 5 with their parents by July 10. That number may include children who told case workers they were traveling with a parent, but were actually separated from them before reaching the U.S. border, something the agency is working to determine, he added.

“It's important to remember that information from children can at times be unreliable,” Azar said.

He insisted HSS will comply with the district court ruling, while adding that it “hinders” the agency’s ability to verify parentage.

“To speed the process, [the Department of Homeland Security] is relocating parents of children age zero to four to facilities that are extremely close to facilities that are in [Office of Refugee Resettlement] care to quickly reunite them,” Azar said.

The secretary confirmed earlier reports that the government is DNA testing parents and children to “quickly and accurately” put families back together. Immigration advocates warn the biological data collection could lead to the surveillance of immigrant children for years to come.

“This is a further demonstration of administration's incompetence and admission of guilt, this further drives home the point we've been saying. They never registered parents and children properly,” RAICES communications director Jennifer Falcon told CNN.

The government has until next Tuesday to reunite young children with their parents. HHS must also reunite children ages five and up with their families by July 26, per the district court ruling. After reunification, the parent and child will be transferred back into the custody of DHS, according to Azar.