Something went boom in the night Tuesday, but no one seems to know what it was, the North County Times reported.
The boom seemed especially powerful along the coast, where residents reported windows, doors and houses shaking at about 10 minutes before 8 p.m.
There was speculation that the sound and accompanying sensation came from a supersonic jet, officials with the Federal Aviation Administration and the U.S.Geological Survey said Wednesday.
Navy officials said they knew of no aircraft activity Tuesday night that might have caused the boom. Marine officials said they would research whether their aircraft might have been responsible.
The FAA says similar sounds made earlier this year are believed to have come from military jets.