Four people have been examined by medical personnel after a white powdery substance arrived at a Hillary Clinton campaign office in New York and they have reported no health issues.
Campaign spokesman Glen Caplin said federal and local officials determined the substance was non-hazardous but he provided no further details.
Police said preliminary tests showed the substance found yesterday in an envelope at Mrs Clinton's Manhattan office, where mail is received, was not harmful.
A police spokesman declined to identify what the substance was.
The envelope arrived around 5.30pm local time on Friday.
It was taken to Mrs Clinton's Brooklyn headquarters and the 11th floor there was evacuated.