The erroneous disclosure was only recently discovered, the people said. The IRS is working with officials from the Treasury Department, Justice Department and Department of Homeland Security on the administration’s response. 

The IRS confirmed The Washington Post’s reporting in a court filing Wednesday afternoon. Dottie Romo, the tax agency’s chief risk and control officer, wrote in a sworn declaration that the IRS provided confidential taxpayer information even when DHS officials could not provide sufficient data to positively identify a specific individual.

Federal law mandates strict protections of the identities of taxpayers, including the sharing of data within the federal government. Undocumented immigrants have for years paid taxes with assurances from the federal government that doing so would not result in them being targeted by immigration enforcement.