Loud booming noises were reported over the weekend in Muskego, but police are unsure of what it was.
Muskego police posted on Facebook Sunday afternoon, stating that the department had received several reports of loud booming noises within the city. The department said the booming "rattled the windows of several homes."
According to police the noises were heard over a wide area including Big Bend, Vernon, Waukesha and Wind Lake.
"Investigating officers were unable to determine a source of the sounds or any evidence that they originated in Muskego," said the department. "As of this time, we have not received any reports of damage or injuries from citizens."
The Associated Press reported the booms might be the results of a rare natural phenomenon known as "frost quakes."
They happen when moisture in the ground suddenly freezes and expands.
Police said there weren’t any reports of damage.
National Weather Service Meteorologist Chris Stumpf told the AP that frost quakes are a reasonable explanation for the sounds.
Police do not believe there is any danger to the public.