The US Federal Bureau of Investigation (FBI)’s Joint Terrorism Task Force is leading a probe into a suspicious letter that has been sent to Republican presidential front-runner Donald Trump’s son.
The mail, addressed to Eric Trump, was opened by his wife on Thursday and contained a threatening letter accompanied by a white powder.
A source close to the investigation told CBS News that the letter had a Massachusetts postmark and warned that if the New York businessman doesn't withdraw from the race, then the kids will be harmed.
The handwritten note said: "If your father does not drop out of the race, the next envelope won't be a fake." It was signed "X."
Preliminary field tests all showed that the substance was not hazardous, but the material had to be sent to the lab for further tests.
The New York Police Department (NYPD) also confirmed the news, adding “the letter has been removed and is being examined by law enforcement authorities. No injuries have been reported in connection with this incident.”
Although Trump has been under protection by the US Secret Service for several months now, a source briefed on the investigation noted that the protection only extends to the real-estate mogul himself at the moment.
The entire Trump family has been given a series of instructions including a review of how to properly handle mail, according to the source.
Protocol requires Trump security personnel to call local police in any emergency. In this particular situation, the NYPD immediately notified the Secret Service and both groups are still investigating the letter.
The Secret Service is also investigating a recent cyber attack on Trump, during which some of his files and private information have been hacked and published on the internet by the hacktivist group Anonymous.
"The US Secret Service is aware of the internet postings of Candidate Donald Trump’s personal information. We are working with the Federal Bureau of Investigation in this matter," a Secret Service spokesperson said.
Trump's campaign has been marked with controversy ever since it started last year and the former realty TV star has raised many eyebrows by his racist and and Islamophobic remarks.
He is currently leading the GOP field having won 678 of the 1,237 delegates required for his party's nomination in the November election.