A window-rattling, house-shaking boom was heard on Bainbridge Island and across Kitsap County shortly after 7 p.m. Wednesday.

The source of the sound was not immediately known.

Reports on social media said the boom was heard all across Bainbridge Island, from Port Madison to Wing Point to other locations to the south. Residents near Crystal Springs, Pleasant Beach, and Strawberry Park also reported the boom.

On Facebook, people living in Poulsbo, Bremerton, Kingston, Keyport, Seabeck, Manchester, and Port Orchard also reported hearing the noise.

Social media theories on the big bang varied.

Some said it sounded like an explosion, or thunder. Another said the sound was reminiscent of the Motel 6 gas explosion in Bremerton five years ago.

A Bremerton resident on Facebook said he heard it “On 10th and Pennsylvania and our s*** got ROCKED.”

A Poulsbo resident said she was in her garage with her dad and ran into the house after the noise to see if something had fallen over and crashed.

There were no immediate reports of an earthquake in the area from the Pacific Northwest Seismic Network at the University of Washington.