The House Oversight Committee voted Tuesday to subpoena Clark Kline, the former director of the White House’s Personnel Security Office, as part of the committee’s investigation into White House security clearances.

Kline previously supervised Tricia Newbold, a White House employee who Democrats described Monday as a government whistleblower. Newbold testified before the House Oversight Committee last month and said she knew of 25 people whose security clearances were denied due to red flags in their backgrounds, but who were later given security clearances anyway without proper explanation.

The 22-15 vote to subpoena Kline fell along party lines, Axios reported.

House Oversight Committee Chair Elijah Cummings, D-Md., said Monday in a letter sent to White House Counsel Pat Cipollone that Kline’s subpoena would be only the first if officials don’t cooperate with the committee’s attempt to investigate the security clearance process.

Ohio’s Rep. Jim Jordan, the highest-ranking Republican on the committee, framed Cummings’s decision to share parts of Newbold’s testimony as politically motivated and questioned the timing of her testimony, which took place on a Saturday morning. Cummings said the abrupt scheduling was a result of White House attempts “to block these witnesses from cooperating with the committee” and an attempt to protect Newbold’s rights as a whistleblower.