Police investigating suspicious envelope found at Clinton campaign office

An envelope containing a white powdery substance was sent to one of White House hopeful Hillary Clinton's campaign offices in New York, with police ruling out any danger.

The envelope was first delivered to Ms Clinton's offices in Manhattan, where campaign workers then transferred it to her Brooklyn headquarters, New York Police Department Lieutenant Thomas Antonetti said.

"The preliminary investigation determined that it was negative in terms of containing a hazardous substance," he added, and noted the Department of Health was conducting further evaluation to determine the nature of the substance.

Lt ntonetti said the envelope also contained writing, but no death threats.

"We're trying to determine what the substance was. For right now, we can at least rule out any poisonous or deadly nature of the substance," he said.