The review comes after all 16 felony charges against the Empire star for allegedly lying to police were dropped on Tuesday in exchange for community service and forfeiture of his $10,000 bond payment.
A hearing Wednesday to expunge Smollett's criminal record was delayed.
A spokesperson for the FBI's Chicago office declined to comment on the report, ABC7 reports.
A source also told Us Weekly that "there is an active federal investigation" into how Smollett, 36, "received an unusually favorable plea deal. Basically, there is a probe to decide whether or not foul play was involved in his bargain with prosecutors."
ABC7 obtained the Chicago Police Department investigative file for the Smollett case as part of a Freedom of Information Act request on Wednesday; CPD released those records not realizing they were part of a judge's order from Tuesday to seal all criminal records related to the case, according to CPD spokesman Anthony Guglielmi. Once the department was made aware that the records were part of the judge's order to seal, they reportedly stopped the release of any other documents.
While Cook County State's Attorney Kim Foxx, who earlier recused herself from the case, defended her office's decision to drop all charges, officials in her office circulated a memo that raised fresh questions about the deal's validity.
The email, obtained by ABC7, asked Cook County prosecutors for examples of cases where charges were dropped under circumstances similar to Smollett's.
"Nobody is in trouble, we are just looking for father examples," the email read, in part.
Foxx had recused herself from the case a week prior to Smollett being charged in February after speaking with a "relative" of Smollett, but not Smollett himself.
In January, Smollett alleged that he was the victim of a racist and homophobic attack in Chicago. During the investigation, which Chicago police initially treated as a hate crime, he was arrested for allegedly staging the ordeal and indicted on 16 felony counts for allegedly filing a false police report. He denied all allegations against him.
On Tuesday, Smollett claimed in a press conference that he had been "truthful and consistent" on every single level since day one."
"I would not be my mother's son if I was capable of one drop of what I've been accused of. This has been an incredibly difficult time, honestly one of the worst of my entire life, but I am a man of faith and a man of knowledge of history and I wouldn't bring my family through this, I just wouldn't," he added.
Smollett's family and a few of his co-stars, including Taraji P. Henson and Gabourney Sidibe, supported the actor following Tuesday's turn of events. Meanwhile, Chicago Mayor Rahm Emanuel and CPD Superintendent Eddie Johnson spoke out against the State's Attorney's office for dropping the files against a man they believed to be guilty.
The prosecutor also believed Smollett was guilty, but said the outcome in the case was not unusual.