Suspicious letter sent to Trump son in NYC; Anonymous targets Donald Trump

CENTRAL PARK SOUTH, Manhattan -- A law enforcement official said 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 said the envelope sent to Eric Trump's apartment at Trump Parc East on Central Park South on 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.

"At approximately 7:15 p.m., the NYPD responded to a residential building at 100 Central Park South to investigate a report of a suspicious letter received by a tenant. The letter has been removed and is being examined by law enforcement authorities," the New York City Police Department told ABC News.

The Trump Organization source, however, confirmed to ABC News that the letter was sent to Trump's 14th floor apartment.

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.

Also on Thursday, the group "Anonymous" claimed it had hacked Donald Trump. Anonymous released what it claimed was Trump's Social Security number, his cell phone number, as well as his his birth date, children's names, and company address.

Trump's campaign issued a statement to ABC: "The government and law enforcement authorities are seeking the arrest of the people responsible for attempting to illegally hack Mr. Trump's accounts and telephone information."

A government official confirmed to ABC News that federal authorities are investigating.

The Associated Press contributed to this report.