He said an internal investigation had begun as part of standard procedure for allegations of information leaks.
Smollett's attorney Mark Geragos says police have been insidiously working to ruin Smollett's case and his image.
Smollett has maintained his innocence and denied all allegations against him, as producers of the FOX drama series made the decision to cut his character off the final two episodes of Season 5 to avoid further production disruptions during the investigation.
The grand jury returned two indictments for Smollett, one stemming from his initial report of the attack and another from a second interview he gave police.
"I will also add that there were several agencies briefed with information during that time and some of the information that went out was not factually accurate", Guglielmi told ABC News on Thursday evening.
The nurse, whose identity was not revealed, said she never accessed Smollett's chart.
The police department is looking into who was the culprit leaking information, which they state is "inaccurate", to the media.
Jussie Smollett remains a sore spot for the city of Chicago, following the termination of dozens of Northwestern Memorial Hospital employees who are accused of having gained unauthorized access to the actor's medical records during his treatment at the hospital. "She's appealing and believes other [sic] may have been fired for simply scrolling past the name as well".
Police Superintendent Eddie Johnson held a press conference on February 21 calling Smollett's conduct "despicable". He has since been released on a $100,000 bond.
Smollett is charged with disorderly conduct, a class 4 felony after police said he filed a false report.
Smollett himself was later arrested, after Chicago police determined that the incident was a hoax that Smollett allegedly orchestrated.
The blast radius from the alleged racist and homophobic attack on Jussie Smollett continues to grow - and we don't mean the actor's future onEmpire or his next court appearance.