Loud booms were heard by many overnight and so far explained by none.
It turns out, the booms were heard not just here, but across the country.
The Vanderburgh Sheriff tells 14 News that it was around the area near Green River and Lynch where they received most of these calls about this strange boom.
It happened yesterday evening, and crews investigated, but authorities and people who heard it are still scratching their heads.
"The sound was like a war bomb," Stacy Lowery said.
Lowery who lives on Old Coal Mine Road in Newburgh had just put her kids to bed and was sitting on the couch when she heard it.
"A huge explosion, like definitely knew it wasn't a firecracker going off. I've never heard anything like it, very disturbing," Lowery said.
Lowery wasn't the only one.
Evansville Dispatch got several calls between 9:30 and 11 Monday night reporting an explosion.
"We obviously dispatched cars. I believe the EFD dispatched crews, the EPD. At the end of the day, we're not able to find anything," Sheriff Eric Williams said.
Crews scoured the area, but didn't find anything.
"It had to be something a little bit different than the typical explosion," Sheriff Williams said.
It wasn't an earthquake. The USGS doesn't have reports of any activity in our area.
Some people have suggested a nearby mine was firing off explosions. But when we called Vigo, which is opening a mine near Boonville, they said their permit does not allow them to blast from dusk until dawn.
The Air Force says it wasn't performing any military drills, either.
Authorities say, at least for now, it will remain a mystery.
"We're going to write it off as the unexplained at this point until somebody gives us an explanation," Sheriff Williams said.
Interestingly, there have been reports of unexplained booms from Arizona to Rhode Island. No one has been able to explain them.