Washington (CNN) Two Democrats on the Senate Armed Services Committee are raising concerns about the US Air Force's investigation clearing four-star General John Hyten, President Donald Trump's nominee to become vice chairman of the joint chiefs of staff, of allegations of sexual misconduct.

While CNN reported this week that no evidence or information had been found to substantiate nine allegations made against Hyten by a junior female officer, Sens. Tammy Duckworth of Illinois and Kirsten Gillibrand of New York, who is also a 2020 presidential candidate, have raised questions about whether the probe was handled properly.

"While I think the investigation was done in a very professional way, I'm concerned that Gen. Hyten might have received preferential treatment. Unlike other military officers who have received similar allegations, he was allowed to stay in his position whereas other folks have actually been suspended from their duties while an investigation was ongoing -- and then reinstated if they were cleared -- but that's not what happened here," Duckworth told CNN.

She also said Hyten's accuser should be given the chance to speak with committee members if she chooses.

"Whenever you have an allegation of sexual misconduct, especially in the military, the victim should be empowered and deserves to be heard. So if she wants to talk to the Committee, she should be given that opportunity and Senators should make themselves available to listen to her. But that's up to her whether she wants to do that and whether she wants it to happen publicly or behind closed doors," Duckworth said.

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