Shakespeare District Lt. Perry Nigro said the skulls, which were discovered in the apartment of Brian Sloan -- who they say uses the items to make anatomical models -- don't "appear to be anything nefarious at this time," The Chicago Tribune reported Wednesday.
However, Nigro said the skulls were taken to the Cook County medical examiner's office for examination and Grand Central Area detectives were conducting a death investigation.
Nigro said the skulls were reported by a man who had visited the apartment intending to purchase a mannequin from Sloan.
Sloan said he sells the skulls on Internet auction site eBay to doctors, medical students and other collectors seeking to use human bones for anatomy study. He was not arrested.
"They (police) wanted to make sure I'm not some Jeffrey Dahmer they're overlooking," Sloan said.