Federal investigators are looking into whether 'Empire' actor Jussie Smollett is responsible for a threatening letter that was addressed to him and sent to show's Chicago studio about a week before he was allegedly attacked, according to ABC News.

The letter is currently being analyzed in an FBI crime lab, and the U.S. Postal Inspection Service is also investigating the situation, according to federal officials.

Two Nigerian brothers, Olabinjo and Abimbola Osundairo, who were persons of interest in the attack, told authorities that Smollett paid them to stage the attack after getting mad that the threatening letter didn't get as much attention as he wanted. One of the brothers has appeared on "Empire" before, and the other was reportedly Smollett's personal trainer.

The brothers have since issued a public statement saying they are not racist, homophobic or anti-Trump, and saying they are American citizens born and raised in Chicago.

Smollett's attorneys have denied the brothers' claim that he orchestrated the 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," attorneys Victor Henderson and Todd Pugh said in a Sunday statement. "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."

Here's what we know

From CBS News: