Washington (CNN) A Department of Health and Human Services official told senators on Thursday the agency doesn't lose track of unaccompanied minors but rather, it's hard to locate them after they leave their custody.

"There are no lost children. There are some families that don't take our call, that's a big difference," Jonathan White, the assistant secretary for Preparedness and Response at HHS, told senators during a hearing Thursday.

He continued: "Many individuals come out of the shadows to take their child from us and some of them return to the shadows because they are individuals who are living undocumented in the United States in most cases. And they believe they have cause to fear us."

The comments from the official comes after a report revealed the Department of Health and Human Services is not taking responsibility for unaccompanied minors once they're placed with sponsors.

Sen. Rob Portman, an Ohio Republican who chairs the Senate Homeland Security and Government Affairs Committee Permanent Subcommittee on Investigations, slammed White for his comments, saying he was "simply inaccurate."

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