Clintonville, Wis (The Post-Crescent) -- After four days of unexplained loud booms that have roused area residents from their beds with no answers in sight, local officials have hired an engineering firm to try to locate the source of the strange sounds.

The mysterious booms have captured the attention of national media, including reporters from CNN, NBC and a New York Times who swarmed a public hearing Wednesday when city administrator Lisa Kuss announced the city will spend $7,000 to hire Waukesha, Wis.-based engineering firm Ruekert & Mielke, which will place four seismometers around the city.

If the firm finds the epicenter, the next step will be to pinpoint the depth and what is causing it. The cause is likely only a couple hundred feet under the earth's surface, Kuss said.

"It's possible we'll never have a definitive answer," Kuss told about 400 residents at the Clintonville High School auditorium.

The sounds began Sunday and reports to police since then have come in from across the city of 4,600 residents.

Kuss displayed maps showing where calls have come in from residents reporting vibrations and booms -- which they describe as sounding like thunder, underground fireworks or someone slamming a heavy door.

The city set up audio and video recorders overnight Tuesday but didn't capture anything. There was at least one loud boom at 5 a.m. As of 9:30 p.m. Wednesday, no other noises were reported.

Some residents say their house have been particularly hard-hit.

For Holly Beringer, the vibrations have shaken her home, rattling pictures and dishes. She was in the crowd Wednesday with several of her neighbors, who said they didn't have questions for city officials but were curious to hear if they had any answers.

While city officials haven't pinpointed what is happening, they've ruled out many theories, Kuss said, including issues with the sanitary and storm water systems, changes in methane or propane gas levels, blasting from mines, military activity, criminal activity or construction.

They have consulted several geologists, including researchers at the universities in Milwaukee and Madison without any conclusions, Kuss said. She has received emails from across the nation and world, with people offering suggestions and reporting similar occurrences elsewhere.

A similar incident was reported in Marion, near Clintonville, about two decades ago and in Georgia more recently.

"But it didn't last three days and three nights," Kuss said.

Several scared residents asked whether -- and how -- they should prepare for a serious emergency.

The city can't predict if something bigger will happen, but Kuss told people there is no reason to consider evacuating the city and that there are fewer reported booms and vibrations each day.

Some residents joked they should capitalize on the odd phenomenon by selling free shakes with hamburgers and making T-shirts claiming "things are booming in Clintonville."

By JESSIE VAN BERKEL/The Post-Crescent

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