WASHINGTON — Authorities in New York City are investigating a threatening letter sent to the son of Republican presidential candidate Donald Trump, CBS News reports.

A source tells CBS News the envelope sent to Eric Trump contained a suspicious white powder, which has been sent to a laboratory for testing.

The mail went to the Eric Trump at his Manhattan residence at 100 Central Park South, also known as Trump Parc East.

The letter, the source said, warned that if Trump did not withdraw from the race for the GOP nomination that harm would come to the children.