The FBI and the U.S. Postal Inspection Service are investigating a threatening and racist letter Jussie Smollett received before he told police that he was attacked in Chicago, ABC News reported Tuesday. The letter is reportedly being analyzed by the FBI crime lab. According to CBS Chicago, brothers Abimbola and Olabinjo Osundairo told police that Smollett concocted the attack after the letter he received didn’t get a “bigger reaction.” Last week, police announced that their “investigation had shifted” following interviews with the brothers and their release from custody without charges. Police have requested another interview with Smollett.

Chicago police confirmed on Tuesday that a tip stating that Smollett was seen in his apartment building’s elevator with the two brothers on the night of the alleged attack is unfounded. The Empire actor says he was attacked by two masked men who yelled racist and homophobic slurs at him, beat him, and looped a rope around his neck.