NEW YORK (AP) — The New York City police and the FBI are investigating a threatening letter sent to the Manhattan apartment of Donald Trump's son, Eric, a law enforcement official said.

The envelope sent to Eric Trump's apartment Thursday contained a white powder, but preliminary tests indicated the substance was not hazardous, according to the official, who was not authorized to disclose the name of the person targeted by the threat and spoke to The Associated Press on condition of anonymity.

In a statement, the police department confirmed that it had reported to a Trump building on Central Park at 7:15 a.m. to investigate a suspicious letter received by a tenant but didn't name the recipient.

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.