Police and other emergency responders raced to MILEY CYRUS' house Wednesday night after someone called 911 to report a HOME INVASION.  They also said SHOTS may have been fired.  Police set up a perimeter and even had a helicopter flying over the house.  But they soon realized that NOBODY WAS HOME.  (Here's video.)

Police believe someone pulled a prank called SWATTING, which is becoming pretty common.  It's when someone tries to get a major police response by falsely reporting a serious crime.  Obviously, whoever did it will be arrested and prosecuted if caught.  It's not clear where Miley was, but in recent days she's been spotted in Philadelphia, where her boyfriend LIAM HEMSWORTH is working on a movie.