Two staffers at the Office of Management and Budget (OMB) tendered their resignations after voicing concerns over the withholding of military aid to Ukraine by the U.S. The freezing of military assistance to Ukraine has been the keystone of the House impeachment charges against President Donald Trump; as revealed on Tuesday.

The three House committees that held the closed-door depositions of witnesses released the transcripts of interviews with the Acting Assistant Secretary of State Philip Reeker, who is handling European and Eurasian Affairs, and also senior OMB official Mark Sandy.

“The testimonies from Ambassador Reeker and Mr. Sandy continue to paint a portrait of hand-picked political appointees corrupting the official levers of U.S. government power, including by withholding taxpayer funded military assistance to Ukraine, to further the President’s personal political agenda,” three Democratic House committee chairmen said in a statement.

House Intelligence Committee Chairman Adam Schiff (D-California), Foreign Affairs Committee Chairman Eliot Engel (D-New York) and Oversight and Reform Committee Chairwoman Carolyn Maloney (D-New York) said Sandy had implicated the president in withholding aid, pointing to the comments that Acting White House Chief of Staff Mick Mulvaney made to him.

“Mr. Sandy confirmed that he was told by the office of Mick Mulvaney, the Acting White House Chief of Staff, that the President himself had directed the hold on security assistance to Ukraine. However, he was provided no other reason or justification for the hold when he was directed to implement it,” the Democrats said, noting that he “raised concerns” that a delay of aid may violate the law.

Sandy testified that two staffers resigned; one in the legal division, resigned partially due to frustrations with the unexplained aid freeze, according to a transcript of his testimony released Tuesday.

Sandy recalled that one individual, who resigned had “expressed some frustrations about not understanding the reason for the hold,” according to the transcript, but he noted that he was “reluctant to speak to someone else’s motivations.”

He was also asked whether the OMB legal division employee said they were leaving “at least in part because of their concerns on frustrations about the hold on Ukraine security assistance.”

“Yes, in terms of that process, in part,” Sandy responded.

The officials were not named in the transcript.