New York, Oct 22 (IANS): Democratic presidential nominee Hillary Clinton's campaign office in New York was evacuated after receiving a letter with a suspicious "white powdered substance", according to officials.

However, the New York Police Department (NYPD) has confirmed that the substance tested negative for harmful substances in a preliminary investigation, CNN reported.

The envelope was first delivered to Clinton's midtown Manhattan office on Friday evening, said Lt. Thomas Antonetti of the NYPD. It was then transferred to her Brooklyn headquarters.

Workers evacuated the 11th floor of the Brooklyn office later.

The initial report indicated that the envelope was opened in the Manhattan office and then passed on to her headquarters in Brooklyn. However, it was not clear why the opened envelope was transferred.

The NYPD along with the US Secret Service and the Office of Emergency Management is probing the incident, CNN added.