A loud, booming noise that sounds louder than a firecracker explosion has residents – and scientists – of a Southern California town baffled.

The Pasadena Star-News reported Tuesday that the Alhambra Police Department has received reports of more than 100 reported explosions since Feb. 15. Christopher Paulson, Alhambra director of administrative service, said the highest reports of the noise have come from the northeastern part of the city.

The city had reached out to the Los Angeles County Department of Public Works and the Alameda Corridor-East Construction Authority to see if the noises had come from any of their projects, but Paulson said they were not the cause of the noise not had they heard the reported loud booms.

Susan Saunders has been living in Alhambra, located eight miles from downtown Los Angeles, for the last 47 years. She told the Pasadena Star News she had never heard anything like it before and has been hearing the noises sporadically since February.

“It’s frightening,” Saunders said. “We never know when it’s going to happen or where it’s coming from.”

Saunders described the noise as a loud, booming sound louder than a gun shot with more force than a firework which leaves no trace that an explosion had occurred.

Alhambra officials had even asked Caltech scientists to see if there was any report of any unusual seismic activity at the time the noises were recorded.

Dr. Jennifer Andrews, staff seismologist at Caltech, told the Pasadena Star News that sensors had picked up forces coming from the “peals of thunder of fireworks” but found nothing abnormal about the activity.

Alhambra City Manager Mark Yokoyama expressed his frustration in the mysterious booms.

“No one has seen the cause of the booms, smelled it or found remnants of fireworks,” Yokoyama said, “and the calls we get don’t have enough specificity for us to find the source.”

Saunders is interested to see how long the booms will be a mystery. But whether the noise is something extraterrestrial, she expressed some doubt, according to NBC Los Angeles.

"I believe that anything's possible, but I don't think these are aliens," Saunders said.

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