The Air Force’s Office of Special Investigations is leading an investigation into alleged misconduct by Col. Ryan Marshall, who was fired from command of the 621st Contingency Response Wing on Wednesday.

Maj. George Tobias, the public affairs director for the Air Force Expeditionary Center, confirmed in an email Thursday that Marshall is under investigation by OSI.

“Please understand that while the investigation is ongoing, additional details surrounding the alleged misconduct cannot be released to ensure the integrity of the process,” Tobias said. “Airmen are innocent until proven guilty.”

OSI spokeswoman Linda Card said the investigation was recently opened and is ongoing, and no charges have been preferred at this point. She said she could not comment on what the alleged misconduct involved.

Tobias later said in an email that Marshall had declined to comment.

Marshall was relieved of command by Air Force Expeditionary Center commander Maj. Gen. John Gordy after Gordy “lost confidence in Marshall’s ability to continue serving in a leadership position due to alleged conduct unbecoming an officer,” according to a Wednesday release.

The 621st is located at Joint Base McGuire-Dix-Lakehurst in New Jersey. Col. James Hall, the wing’s vice commander, is now serving as interim commander of the 621st.

The Expeditionary Center is the Air Force’s Center of Excellence for advanced mobility and combat support training and education. It also directly oversees missions including en route and installation support, contingency response, and building up partners’ capacities.

The 621st is responsible for “advising partner nations and joint partners; directing theater-wide command and control; and projecting mobility airpower around the globe for contingency and humanitarian operations,” according to Marshall’s biography.