Kaye Olson said she was woken up by the strange sound around 5 a.m. At first, Olson said she thought it was a plane, but the noise was too rhythmic to be an engine.
She said the sounds occurred about 10 seconds every minute and finally stopped altogether after half an hour.
Later in the day, Olsen spoke with some neighbors, who also heard the noise and one suggested it was the Labadie Power Plant.
An Ameren spokesperson confirmed that the noise indeed came from the plant. He said it was steam being released, a safety measure that doesn't happen very often.
The spokesperson also apologized that the event happened so early in the morning.