Dozens of residents in Shelby County reported hearing a big boom Monday morning, but authorities are unsure what caused it.

The boom was heard and felt in parts of Pelham, Alabaster and Helena.

Alabaster police said they received a call about an explosion but had no reports of damage.

Helena police were hearing from several concerned citizens but had no reports of injuries. City officials were in the process of contacting Public Works to find out if any work or blasting was being performed nearby.

Helena Fire chief Peter Valenti said the first call about the boom happened around 9:30 a.m.

"There is no physical evidence of any explosions in our area," Valenti added.

Valenti heard and felt the boom himself. He said it sounded almost like a car door slamming and he felt a slight vibration. He suspected it was a sonic boom or possibly an earthquake.

"It was felt pretty much all over Shelby County," Valenti said. "I am thinking a sonic boom but according to 911, there is no military activity in the area. So, my best guess is it was a sonic boom of an unknown source."

The quarry in Helena was not blasting Monday morning, and Valenti said the quarry would not blast something so large that it would be felt all the way in Alabaster. He also said no other permits for blasting had been issued.

The United States Geological Survey did not have reports of an earthquake anywhere in Alabama Monday morning.

The Bama Boom Tracker showed reports from Crosscreek Trail, in Pelham, Helena City Hall and Newgate Road in Alabaster. Valenti said there were also reports of the boom being felt in Calera.

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