Authorities in Tennessee spent hours looking for the source of a “loud explosion” and ground shaking reported by residents.

The Clarksville Police Department said on Facebook on Sunday, Sept. 5, that its 911 dispatch had gotten multiple complaints about a “loud explosion” at around 9:50 p.m. local time on Saturday and that some people said they felt the “ground shake,” Fox News reported.

“The sound was heard across many parts of Montgomery County but there have been no reports of any injuries or property damage. The Clarksville Police Department, Fire Department, Montgomery County Sheriffs Office and Emergency Medical Services (EMS) searched for a couple of hours but were unable to locate the source.,” the department wrote

In one security footage, Heather Rooney captured a bright flare at the same moment as the sound. The boom can be heard in the distance in another house surveillance video. Dee Boaz assumed it was a boat explosion and searched the Cumberland River but found nothing. “It was just so odd,” Boaz added.

She smelled a weird odor as well. “Not a normal kind of odor,” Boaz explained.

The U.S. Geological Survey did not detect an earthquake in the vicinity, according to WKRN.

One of the most prevalent hypotheses claimed it came from Fort Campbell in Kentucky, home to the 101st Airborne Division that straddles the boundary between Clarksville and Hopkinsville.

Fort Campbell, however, was on a “four-day weekend due to the Labor Day holiday” at the time of the explosion, according to the Clarksville Police Department, and did not appear to be “conducting any type of training or exercise.”

Some had made fun of the issue, comparing it to the famed UFO incident at Roswell in 1947, when the Roswell Army Air Field announced the discovery of a “flying disc” on a nearby property, Newsweek reported.

Others had linked it to the bizarre occurrence in Clintonville in March 2012, when villagers heard a succession of unexplained noises for four days. However, USGS geophysicist Paul Caruso said, “All throughout the eastern United States, even small earthquakes are felt great distances … It’s because the rocks are just really old. They transmit the energy really well.”

“Currently, this seems to be some sort of unknown phenomena until someone reports actual damage,” the police department wrote on Facebook.