Norwich Fire Chief Tracy Chawgo said the building had conducted a fire drill about ten minutes prior to an actual alarm sounding and the building being evacuated a second time. He reported a ventilation fire detector sounded after smoke began fill an air shaft. The Norwich Police Department closed down streets in the immediate area of the building as firemen did a floor to floor search for the cause of the smoke. Finally firemen inspecting the building’s roof identified a shorted-out computer panel, near an intake fan, as being responsible. ..