Three court employees were temporarily quarantined and decontaminated after a white powder fell from an envelope about noon Monday in the Niagara County Courthouse in Lockport.
Testing showed the material was "98 percent vitamin C powder and 2 percent talcum powder," said Christian Peck, Niagara County public information officer. Peck said the envelope was mailed to a court office from a state prison.
A county employee who was present said the second floor of the building, where the court offices are located, was cordoned off, the air handling system was shut down and the building was evacuated.
Hazardous materials crews from the Lockport Fire Department, the county and the Niagara Falls Air Reserve Station investigated.
Peck said the building will be open as usual Tuesday.