The mystery behind four days of unexplained shaking and odd sounds rattling Clintonville, Wis., has been solved.
The cause? A "swarm" of minor earthquakes amplified by the unique bedrock beneath the state of Wisconsin, CNN reported Friday.
The strange sounds -- variously described as rattling pipes, clanging metal, thunder or firecrackers -- have continued on and off since early Sunday night in one part of the small town of 4,600, located about 180 miles northeast of Madison, according to Green Bay TV station WBAY.
More from GlobalPost: Clintonville booms to be investigated (VIDEO)
Speaking to Clintonville residents Thursday night, U.S. Geological Survey officials said they believe a 1.5-magnitude earthquake struck the area earlier this week about four miles under the surface, CNN reported.
The USGS attributed the shaking and strange popping noises to a "swarm of microquakes" amplified by soil and granite underneath the city, USA Today reported.
But just because the mystery is solved doesn't mean residents aren't still looking for answers.
Many are still concerned, especially about the source of the booming noises, how long they might last, and if there's a possibility of the vibrations getting stronger, WBAY reported.
"There's people like me who have damage. There's people like me who are still afraid," Sharon Binger told the TV station. "And, you know, they're still not giving us any answers and all of the sudden they have all these experts. Never seismatic -- boom, boom, boom. Now all the sudden they are. I don't know."