Washington (CNN) The top Democrat on the House Intelligence Committee said Thursday Democrats made the "first move" in protecting special counsel Robert Mueller's investigation by sending letters ordering top Trump administration officials to preserve documents connected to the probe.

The expected new chairmen of the House Judiciary, Intelligence and Oversight committees sent letters on Wednesday ordering top Trump administration officials to preserve documents connected to Mueller's investigation and the firing of Attorney General Jeff Sessions.

Schiff, the expected new leader of the Intelligence Committee after Democrats took back the House Tuesday, told CNN that this is the "first move" Democrats have taken to prevent Mueller from potentially being fired.

"But if the President effectively undermines the rule of law and causes the special counsel to be fired or an abrupt or partisan end to this investigation, then it will fall on Congress to find out the facts itself, to get those facts from the Justice Department, to continue our own investigation so that we can tell the country exactly what happened," Schiff said Thursday in an interview on CNN's "The Lead with Jake Tapper."

President Donald Trump insists publicly he has no plans to fire Mueller, but has worked to discredit the investigation, calling it a "witch hunt."

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