A review of the White House’s decision to block aid to Ukraine revealed that staff sent hundreds of emails attempting to justify the decision after the impeachment process started.

The White House Counsel’s Office launched an investigation into the decision to temporarily withhold military aid to Ukraine after the House announced its impeachment plans. Emails recovered in the probe show that chief of staff Mick Mulvaney had email exchanges in August in which he tried to sort out a justification to withhold the aid, according to a Sunday report from the Washington Post.

The emails recovered are confidential, but a source told the Post that some of the material paints an unflattering picture of White House operations that could embarrass President Trump. An Office of Budget Management source, however, classified the conversations as routine and noted that the talks were mostly in regard to the Budget and Impoundment Act, a law that requires the executive branch to spend money as appropriated unless Congress agrees there is justification to reverse the funding.

Congress had approved the $400 million military aid package that Trump withheld in July. That funding was eventually distributed per Congress’s appropriation. Because the funding was only temporarily withheld, OBM claimed the White House did not need Congressional consent.

Mark Sandy, the only OBM employee to testify in the impeachment hearings, said in his closed-door testimony that the process was “unusual.”

Trump’s decision to withhold military aid has been the basis of the Democratic Party’s impeachment argument. House Democrats alleged that Trump withheld aid to force a Ukrainian investigation into former Vice President Joe Biden and his son Hunter Biden, putting national security at risk.