A possible human organ was spotted floating in a Detroit wastewater plant — the third discovery in less than a week that has deepened a mystery authorities are trying to solve.

The object was located just before 7 p.m. Wednesday at the Water Resource Recovery Facility, FOX2 Detroit reported. Authorities said it appeared to be an organ, but have not determined if it was from an animal or a human.

On Friday and Saturday, two organs, both thought to be kidneys, were found at the plant in two separate incidents.

"I know in the...past weeks we've had some other incidents. There is an investigation into it right now. The results are still not back from the medical examiner for the origin of the recovered organs in the past week, so it's an ongoing investigation," Detroit Police Capt. Darin Szilagy told FOX2.

The medical examiner will inspect the organs to determine the type and origin of the objects.

The mysterious objects sparked concern about the water treatment, but a spokeswoman for the Great Lakes Water Authority said it doesn’t affect the process because the suspected organs were found in the filtering process pre-treatment.

The Water Resource Recovery Facility, previously known as the Wastewater Treatment Plant, is the largest single-site wastewater treatment facility in the U.S., according to the Great Lakes Water Authority’s website.