Someone is disposing of placentas in the sewage system and authorities in central Illinois just want it to stop.

Workers-Champaig in Urbanan found a placenta Thursday in a filter that keeps large objects out of the sewage treatment plant. It was the third found this year. Officials say it's never happened before. They wonder if a midwife or veterinarian is avoiding the expense of medical waste disposal.

The placenta is an organ that joins mother and fetus and is expelled during birth.

They are potentially infectious, although health officials say the risk to the public is low. State regulations prohibit disposal in sewage systems.

Champaign County Coroner Duane Northrup says he's not entirely sure whether the placentas are human or animal. More testing is under way.