A letter that contained white powder and a threatening message was sent to the Central Park South home of Donald Trump’s son on Thursday.

The envelope with a Massachusetts postmark was addressed to Eric Trump, 32, at his apartment in the Trump Parc East, according to sources.

The letter contained a threatening message that implied that Donald Trump’s children would be hurt if the GOP candidate did not withdraw from the presidential race, according to CBS News.

Eric’s wife, Lara Yunaska, opened the envelope and white powder fell out, prompting police, fire crews and the FBI to respond.

It was not clear what the powder was.

The ominous letter arrived less than a week after an outbreak of violence last Friday at a Trump political rally in Chicago, forcing it to be canceled.

On Monday, a man tried to rush Trump during a speech in Dayton, Ohio.

The real estate mogul has angered immigrants, women, Muslims and others with his fiery speeches on the campaign trail.

Republican leaders, including House Speaker Paul Ryan, have pleaded with Trump to tone down his rhetoric.