The Cobb County courthouse has fully reopened and returned to normal operations after police investigated a "suspicious item" on Thursday afternoon. A spokesperson for the Marietta Fire Department says emergency crews responded to the courthouse complex shortly after midday. Fire officials said an employee was opening a letter when a "powdery substance" was seen. Streets around the buildings were shut down to allow for rescue crews to respond. Most courtrooms were still accessible, but the immediate area was cleared. Officials were able to test the substance quickly and found it to be benign. Since no hazards were found, the courthouse returned to normal operations. The incident remains under investigation.