The FBI is working diligently to track down who sent Jussie Smollett those threatening letters just days before he was attacked in Chicago last month.

According to TMZ, FBI agents have been helping a private agency hired by “Empire” showrunners to develop a vigorous protocol of inspecting mail that comes onto the set. The security measures are being taken very seriously and the team is reportedly wearing gloves during the mail screening process to avoid contaminating any evidence.

The two-part screening process will alert the FBI of any suspicious incoming mail and try to make the connection between any new threats and the original letters received containing hateful drawings and a message that read, “You will die black f-g.”

As previously reported, Smollett and other members on set have since beefed up security. The “Empire” star initially turned down an offer from Fox for extra bodyguards when the first threats were received. In addition to increased security, TMZ has learned production hired extra makeup artists to ensure Smollett looks his best on camera without any visible scars from his attack appearing in any “Empire” scenes.

Local authorities have yet to arrest anyone in connection with the assault but did release surveillance footage of two potential persons of interest. It has also been reported that the police would like to interview Smollett again as part of their ongoing investigation in the case.

On Saturday (Feb. 2), Smollett made his return to the stage in Los Angeles for the first time since his attack. He dismissed rumors that he suffered cracked ribs and told the crowd that he fought off his assailants. “I’m the gay Tupac,” he joked.

Smollett has vowed to work with authorities and says he has been “100 percent factual and consistent on every level” in an official statement about the ordeal.