Bishop International Airport in the US state of Michigan was evacuated and temporarily closed Wednesday morning (local time) after a policeman was critically injured by an unidentified knifeman. Witnesses said one man was led away in handcuffs. No details on the background of incident were initially released. The FBI launched an investigation of the incident, with agents and police officers sweeping the area in and around the facility. The airport is located about 70 miles north of Detroit in the city of Flint.