A loud boom-like noise shook parts of Lakewood, Brighton, Lochbuie, and Elizabeth in Colorado on Monday night. The sound, which residents described as an explosion, has left authorities baffled.

Mysterious Noise Baffles Residents

The boom was reportedly first heard around 9 p.m., local time, on Nov. 20. It was so loud that some people in the vicinity stated that their house and windows shook during the incident.

A few residents took to Facebook to report the matter, while several others called up Denver7, the local news channel, to describe the noise.

"It was just like boom and the trailer shook, and I thought, 'what the heck was that?’”, said Ray Armijo, a resident who has served in the military. "It kind of scared me a bit.”

Armijo also added that the sound did not seem to come from the ground but rather from the air. Another resident, Aleja Moronez, claimed that the noise was so loud that it moved things in her room and some posters fell off the wall.

Lochbuie Police Chief, Tracey McCoy, said that he contacted both the Buckley Air Force Base and Federal Aviation Administration, however, they were carrying out no operations in the area at that time that could have contributed to the sound. The Brighton Fire Department also received several calls from worried residents, but they too could not locate the source.

Booms Also Heard In Other Parts Of United States

Colorado is not the only U.S. state, where residents of several towns have reported hearing explosion-like sounds. In the past few days, the booms have also been heard in New Jersey, Alabama, Idaho, and Detroit.

The residents of the areas are now speculating about the cause of the noise, now referred to as “Bama Boom”, with some attributing it to active meteor showers, deep earthquake, and even an alien invasion.

The Birmingham National Weather Service originally hypothesized that the sound could have come from a supersonic aircraft or that a meteor, from the Leonid meteor shower, which peaked on Nov. 17 and 18, could have broken the sound barrier. The latter, however, was refuted by the head of NASA's Meteoroid Environment Office, Bill Cooke.

Cooke said that the noise could have been caused by a ground explosion, supersonic aircraft, or probably a bolide, which is a large meteor that explodes in the atmosphere, but is unrelated to the Leonid meteor shower.

The U.S. Geological Survey's Lakeview Retreat near Centreville, Alabama had also picked up a boom sound. However, seismic data indicated that the boom was not the result of an earthquake-related event.

At present, authorities are still investigating the incidents and are trying to figure out the actual reason that led to the booms, which have been heard at various points throughout the month.