The Blast reports that the FBI is investigating who sent the letter, regardless of whether or not the threat was legitimate or part of an orchestrated scheme involving Smollett. Sources told the news outlet that the possible charge would be "mailing threatening communications."
According to the news outlet, the charge states that "whoever knowingly so deposits or causes to be delivered...any communication...addressed to any other person and containing any threat to kidnap any person or any threat to injure the person of the addressee or of another, shall be fined under this title or imprisoned not more than five years, or both."
Ultimately, whoever sent the letter could be fined and sentenced to five years in prison, if prosecuted to the full extent of the law.
Days before the alleged attack, a letter containing white powder — which later was determined to be aspirin — was sent to the set of Empire. Smollett described the letter in an interview last week with Good Morning America, saying, "It had a stick figure hanging from a tree with a gun pointing toward it with the words that says Smollett Jussie, you will die."
As previously reported, police are reportedly interested in interviewing Smollett again after the scope of the case "shifted" following the arrest and release of two men suspected of the alleged attack against Smollett.
Smollett's spokeswoman, Pamela Sharp, told local Chicago news outlets Sunday there were no updates "as of now." Another spokeswoman, Anne Kavanaugh, could not confirm if Smollett agreed to another interview.
Police confirmed "developments" in the investigation, although did not confirm reports that Smollett was suspected of orchestrating the highly-publicized attack.
"While we are not in a position to confirm, deny or comment on the validity of what's been unofficially released, there are some developments in this investigation and detectives have some follow-ups to complete which include speaking to the individual who reported the incident," police spokesman Anthony Guglielmi wrote on Twitter Sunday.
Smollett, 36, claimed he was attacked by two men on Jan. 29 outside his Chicago apartment building, saying that the men yelled racial and homophobic slurs, dumped an unknown chemical on him and put a rope around his neck.
Friday, brothers Obabinjo Osundairo and Abimbola Osundairo were arrested and released hours later without being charged after police named them as persons of interest. Guglielmi said they were released after they provided "new evidence."
Law enforcement sources told local news outlets the brothers told detectives that Smollett paid them to take part in the alleged attack and bought the rope found around the actor's neck. They reportedly said they were paid $3,500 before they left for Nigeria on the day of the attack and were promised $500 once they returned to Chicago. They also reportedly said they rehearsed the attack "days" before it happened.
Smollett continues to maintain that he is a victim in the attack. In a statement from his lawyers, he insisted that he did not play a "role in his own attack."
"As a victim of a hate crime who has cooperated with the police investigation, Jussie Smollett is angered and devastated by recent reports that the perpetrators are individuals he is familiar with," the statement from Todd S. Pugh and Victor P. Henderson read. "He has now been further victimized by claims attributed to these alleged perpetrators that Jussie played a role in his own attack. Nothing is further from the truth and anyone claiming otherwise is lying."
They said Smollett will continue to cooperate with police, adding, "At the present time, Jussie and his attorneys have no inclination to respond to 'unnamed' sources inside of the investigation, but will continue discussions through official channels."