TMZ cited law enforcement sources as saying a woman recently filed a report with the Los Angeles Police Department accusing "The Voice" judge of sexual assault.
The identity of the alleged victim, as well as when the supposed incident took place and specifically what Green allegedly did were not immediately known, the celebrity news website said.
TMZ said police have spoken to staff at a restaurant linked to the case, however, it is also unclear if the eatery is where the assault allegedly happened.
Green told the website he has done nothing wrong.
"Nothing ever happened there or anywhere else," Green said, referring to the restaurant.
Authorities said no charges have been filed and the case has not been referred to prosecutors.
A holiday special called "CeeLo's Magic Moment," starring Green and The Muppets, is scheduled to air on TV Guide Network next month.