Police in New York say preliminary tests on a white powdery substance contained in an envelope that was sent to Hillary Clinton's campaign, forcing an office to be evacuated, is not harmful.

A spokesman for the New York Police Department says the envelope was found at Clinton's Manhattan office, were mail is received, around 5:30 p.m. Friday. It was then taken to the 11th floor of her Brooklyn headquarters.

The discovery of the suspicious substance caused that floor to be evacuated. The police spokesman says there have been no reports of illness or injury.

The NYPD spokesman declined to identify the substance other than saying it was not harmful.