NEW YORK - A law enforcement official says New York City police and the FBI are investigating a threatening letter sent to the Manhattan apartment of Donald Trump's son, Eric.

The official says the envelope sent to Eric Trump's apartment Thursday contained a suspicious white powder and a threatening letter. There were no injuries and the official said preliminary tests indicated that the white substance was not hazardous.

The law enforcement official spoke to The Associated Press on condition of anonymity because they were not authorized to disclose the name of the person targeted by the threat.

Eric Trump is the younger of two adult sons of businessman and Republican presidential front-runner Donald Trump. He has been campaigning for his father.

Donald Trump's representatives did not immediately respond to a request for comment.