The city of Chicago has fired 2 security officers involved in dragging a man off a United flight

Chicago's Department of Aviation has fired two of three officers involved in dragging David Dao, 69, off a United Airlines plane in April.

The investigation was conducted by the Office of Inspector General and found that the security officers mishandled the situation. It also found that the sergeant removed facts from the employee report about the incident, The Chicago Tribune reported.

The Department of Aviation ultimately fired the officer who "improperly escalated the incident" and the sergeant who tampered with the incident write-up, according to the report.

The three officers had been placed on administrative leave while the investigation took place.

Officers forcibly removed Dao from the plane when he refused to give up his seat for a crew member. Dao lost two front teeth, broke his nose, and suffered a concussion as a result of being dragged off the plane.

A video of Dao's removal went viral in April, sparking widespread outrage online. The news prompted the US House Transportation and Infrastructure Committee to hold a hearing about airlines' customer-service policies and internal practices.

United Airlines reached an out-of-court settlement with Dao in April, the amount of which was not disclosed.