The source of a mysterious sound heard Sunday afternoon in many parts of the Ozarks is still primarily that — a mystery.

Harrison Police began getting calls about the sound just before 4:45 p.m. Sunday.

The first caller was on West Park Avenue. The woman reported she heard an explosion and felt vibrations, although the explosion sounded a long way off.

An officer on patrol checked in the immediate area, but didn’t locate anything that might have been the source. A report said he spoke to people at the Soccer Complex who also heard it and thought it might have come from the Highway 7 South area.

A few minutes later, a caller on Highland reported hearing it and an officer checked that area, speaking to people on Windsor Drive who said it shook their house.

A caller in Batavia also reported hearing the explosion, but Boone County Sheriff’s Office officials said they didn’t locate a possible source either.

Some people thought it might have been an earthquake. However, the U.S. Geological Survey website shows the nearest earthquake in that time frame was about eight miles southwest of Cherokee, Oklahoma. It was measured at a magnitude of 3.1.

A USGS seismologist said it’s not uncommon for people to hear what sounds like an explosion during an earthquake.

However, she said a 3.1 magnitude quake usually won’t be heard or felt more than 200 kilometers away, or about 125 miles.

Cherokee, Oklahoma, is almost 500 kilometers from Harrison.

Other people thought it might have been a sonic boom, the sound generated when an aircraft breaks the critical speed of Mach 1, which is roughly 760 mph.

But aviation experts say aircraft are usually limited to where they can break the sound barrier and aren’t allowed to over populated areas.

“It’s possible there was a sonic boom from a military aircraft,” Lunsford said in a statement. “If so, it would have made a loud sound like thunder. Depending on altitude, it’s possible that people might have been able to feel it on the ground, or see signs such as dishes or windows rattling.”

Still, he reiterated that the only aircraft capable of going supersonic these days belong to the military.