The House committees leading the impeachment inquiry announced Friday that they had issued subpoenas of three more Trump administration officials.

Office of Management and Budget officials Michael Duffey and Russ Vought were sent letters conveying the subpoenas, as was Department of State Counselor T. Ulrich Brechbuhl.

According to the letters, all three officials had previously communicated to the committees that they would not voluntarily appear for interviews, as the committees had initially requested.

The Democrats are now demanding that Duffy sit for a deposition on Nov. 5, and that both Vought and Brechbuhl appear on Nov. 6.

The OMB was in charge of implementing a freeze that President Trump ordered on congressionally-authorized military assistance to Ukraine. Vought is the acting head of OMB and Duffey is a top political OMB appointee who signed documents OKing the delay in transmitting the military assistance. Those types of documents are typically signed by career OMB officials, CNN reported, a signal perhaps that there was some resistance internally at OMB to blocking aid that had been appropriated by Congress.

Another source claimed to CNN that Duffey personally signed off on the freeze because he was in the process of learning more about the ins and outs of the procedures at OMB.

Brechbuhl was named in the Ukraine whistleblower’s complaint as among the people who may have listened in on Trump’s July 25 call with Ukraine’s President; officials have since reportedly denied that he was on the call. He also came up in the prepared testimony of Bill Taylor, a top U.S. diplomat in Kyiv who said he reached out to Brechbuhl about the frozen aid.

House Democrats so far have had some success in securing testimony from Trump administration witnesses by quietly subpoenaing them ahead of their scheduled interviews. The three officials subpoenaed Friday, however, are among the highest ranking political appointees who have been targeted by the committees for interviews.

The White House has imposed a blanket ban on administration officials cooperating with the impeachment inquiry.