A loud boom was heard and felt in Waterloo and surrounding areas about noon on Thursday, with no official word on a source.

“I just heard/felt a sonic boom in Foster Pond area. Anyone else?” local resident Deb Ruggeri posted on Facebook.

Ruggeri received several replies from Waterloo-area residents who had indeed heard the same noise. Other local residents posted similar messages on Facebook. Workers inside the Republic-Times office at 205 W. Mill Street in Waterloo also heard what could be described as a loud rumble.

Local officials remain unsure of the source, with possible causes being a sonic boom, blasting at an area rock quarry, or the shooting of tannerite — a patented exploding target used for firearms practice.