The Department of Homeland Security has hindered internal investigations amid scrutiny for its handling of President Donald Trump’s aggressive crackdown on immigration, the agency’s official watchdog warned in a letter to Congress.

DHS has been “systematically obstructing” investigations by withholding records, Inspector General Joseph Cuffari said in a letter released Tuesday — hours after Homeland Security Secretary Kristi Noem faced withering bipartisan questioning at a Senate hearing.