(CNN) -- A grand jury has been convened in Cook County, Illinois, in connection with new allegations against singer R. Kelly, according to two sources close to the case.

This comes on the heels of attorney Michael Avenatti announcing last week that he had handed over to the State's Attorney's office a videotape that he says shows Kelly engaging in sex acts with an underage girl.

The Cook County State's Attorney would not confirm the grand jury proceedings or the existence of any new investigation. The office had previously encouraged any alleged victims of R. Kelly to come forward.

Steve Greenberg, an attorney for R. Kelly, told CNN on Monday he had not been notified of a grand jury.

"No one from law enforcement has contacted me or my client regarding any potential investigation," Greenberg said. "Certainly they are aware that I am representing him so if there were any reason to speak to him I would suspect they would have reached out to me."

"Grand jury proceedings are, by law, supposed to be secret, so to the extent people are commenting on what may or may not be going on today are possibly violating the law. Still, I can tell you that I am unaware of any proceedings," Greenberg said.

CNN has seen the VHS tape that appears to show Kelly having sex with a girl who refers to her body parts as 14 years old. Avenatti, who is representing a man he calls a whistleblower against Kelly, says he handed the tape to the Cook County State's Attorney's Office in Chicago last weekend.

"My client knows the identity of the girl and R. Kelly. He identified the two of them on the videotape. He worked for and has known R. Kelly for decades and he met the girl on a number of occasions," Avenatti said.

Greenberg, Kelly's attorney, told CNN after the tape had been handed over that he was not aware of it.

"We are unaware of any new information involving Mr. Kelly," he told CNN. "We have not been contacted by anyone. We have not been informed about any new information by anyone and we have not been contacted by law enforcement."

Tandra R. Simonton, chief communications officer for the State's Attorney's Office would not "confirm or deny an investigation" when the tape was reported last week.

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