Reports: Police investigate threatening note sent to Trump's son

New York police are investigating a threatening letter sent to Donald Trump's son that included suspicious-looking white powder, news organizations are reporting.

"A preliminary field test indicated the substance did not appear hazardous," ABC reported, citing an unnamed source in the Trump organization, but the letter included a threat.

"The letter said: 'If your father does not drop out of the race, the next envelope won't be a fake,' " the Associated Press reported. "It was signed 'X,' according to one of the law enforcement officials, who had seen the letter."

The AP also said, "the handwritten letter was postmarked March 5 from Boston and referenced Donald Trump's presidential bid."