San Diego residents reported seeing mysterious lights hovering in the sky Monday night.

San Diego residents were left scratching their heads after spotting the unusual sight.  Eyewitness photos captured the mysterious bright lights over the Pacific Ocean. Videos of the lights were also posted to social media.

It was not immediately clear what the lights were. A plane? Space junk? Something more sinister? Apparently, there weren't any commercial or military aircraft on radar in the area, so the source of the lights will remain a mystery -- at least for now.