– The confirmation of President Donald Trump’s pick to become the U.S. military’s No. 2 officer could be delayed as senators question how the Pentagon handled sexual assault allegations against him, even though military authorities deemed them insufficient to bring charges.

Trump nominated Air Force Gen. John Hyten, commander of U.S. Strategic Command, to become the next vice chairman of the Joint Chiefs of Staff in April.

Shortly after, an Army colonel who had been relieved of her duties while serving on his staff for allegedly creating a toxic work environment alleged that Hyten had made sexually abusive contact with her on more than a half-dozen occasions, including in a California hotel room during the Reagan National Defense Forum in December 2017.

The allegations — which Hyten denies — prompted a probe by the Air Force criminal investigative service. Based on the results, the Air Force decided not to press forward with a court-martial or any other disciplinary actions against Hyten, who is in charge of the nation’s nuclear arsenal.

“After a comprehensive investigation by the Air Force Office of Special Investigations, there was insufficient evidence to support any finding of misconduct on the part of General Hyten,” Pentagon spokeswoman Col. DeDe Halfhill said. “With more than 38 years of service to our nation, General Hyten has proven himself to be a principled and dedicated patriot.” A senior U.S. military official said investigators spoke to 53 people in three countries and 13 states and reviewed thousands of e-mails.

After interviewing people who previously served under Hyten, investigators didn’t find indications of such behavior with other subordinates, said the military official, who like others spoke on the condition of anonymity to discuss the details of a legal matter. “Did we find a case where the service member says on this date, x happened, and when we looked at it, they were on different continents? We didn’t,” the official said. “So was it physically possible? Yes.”

The Army colonel who made the allegations said she is willing to testify under oath to the Senate Armed Services Committee, which is overseeing Hyten’s confirmation process, preferably in a closed-door session. She described the military justice system that adjudicated her case as flawed and said the alleged incidents merit action by the military as Hyten prepares to ascend to a position of even greater power.

Members of the Senate Armed Services Committee have already questioned the Pentagon about its handling of the case.

In a June 25 letter to acting Defense Secretary Mark Esper, Sen. Elizabeth Warren, D-Mass., and Sen. Tammy Duckworth, D-Ill., said they were “gravely troubled” that the Pentagon designated an Air Force general who was junior in grade to Hyten to decide whether to proceed to a court-martial or other disciplinary measures. Gen. James Holmes, commander of Air Combat Command, who is part of a small Air Force four-star general officer corps along with Hyten, served as the convening authority in the case.