Police 'Not Completely Sure' What's Behind Unexplained Explosion-Like Noises

ALHAMBRA (CBSLA.com) — Residents in Alhambra and nearby cities say they've been hearing explosions during the night over the past several months.

Since February, Alhambra police have received more than 100 reports of explosions, some big enough to reportedly shake homes throughout the area.

Susan Saunders says she's heard the sound about a dozen times, typically at night, which causes her windows to shake and her dog to go crazy.

She says the explosion has more force than a firework, and leaves no residue or smoke.

"It's unexplained," she said. "It's kind of fun, but it's kind of scary, too."

M. Marie Gallego, who has lived near Garfield Elementary School on McLean Street her whole life, says she hears similar noises all the time.

"Usually, they're at night, around like 10 [p.m.] all the way to the middle of the night," Gallego said. "They're just like big boom sounds."

City officials are baffled. One blast even interrupted a council event.

"A very short but sharp, explosive sound," said Christopher Paulson, Alhambra public information officer. "We all flinched."

The city contacted the Los Angeles Department of Public Works and seismologists at Caltech, but no one has been able to figure out the origin of the sound.

"We want to know what it is, just so we can get to the bottom of it," said Paulson.

Residents from neighboring cities including South Pasadena and San Marino have reported similar noises, with many attributing the reports to fireworks.

Residents from San Marino, South Pasadena and El Monte said they have heard similar noises, but they can't determine the source.

While authorities continue to try to pin down a source, Alhambra Police Sgt. Jerry Johnson says there are few clues so far.

"We have not been able to isolate the sounds or even positively identify that it is even a firework," he said. "We're just not completely sure what exactly these noises are."

Officials with both Alhambra Fire and Southern California Edison have told police they haven't received any reports of blown transformers or power outages.