(Newsweek) – A mysterious boom was felt and heard by residents in some parts of San Diego and the surrounding areas on Wednesday, according to reports. Several people from Del Mar to Chula Vista posted on social media early Wednesday afternoon that the boom had shaken doors and furniture, as well as startling pets, ABC 10 reported. “Felt it in La Jolla / Windansea – even my dogs started barking!” one Twitter user, @eith3r_0r, posted.

Many people suggested that the sound could have been produced by an earthquake. “Mysterious boom heard along San Diego Coast. And I thought it was an earthquake,” Twitter user, @adolfo_v, wrote. However, the U.S. Geological Survey (USGS) said an earthquake was unlikely to have been the cause of the boom.

“The last earthquake in the vicinity was at 4:16 a.m.,” said Paul Laustsen, a USGS spokesperson. This tremor—which struck near Corona—measured just 2.9 on the Richter scale. Laustsen then suggested that the noise could have resulted from the sonic boom of an aircraft. This occurs when an aircraft breaks through the sound barrier, generating a sound like an explosion or a thunderclap. FULL REPORT