House Judiciary Chairman Jerry Nadler (D-NY), Oversight Chairman Elijah Cummings (D-MD) and Homeland Security Chairman Bennie Thomas (D-MS) are demanding documents related to the recent spate of firings at the DHS.

“We are deeply concerned that the firing and forced resignation of these officials puts the security of the American people at risk,” they wrote. “We are also concerned that the President may have removed DHS officials because they refused his demands to violate federal immigration law and judicial orders. Moreover, we are concerned by reports that, even as he has removed the Department’s leadership, the President has sought to empower a White House aide, Stephen Miller, to ‘be in charge of handling all immigration and border affairs.’”

The chairmen also say that the White House has declined to make Miller available for committee testimony.

In the past few weeks, DHS Secretary Kirstjen Nielsen, DHS Undersecretary for Management Claire Grady, Secret Service Chief Randolph “Tex” Alles and ICE chief nominee Ronald Vitiello all got the axe, leaving a few other officials in a precarious position.

Read the letter here:

