R&B superstar Rihanna had to cut short her concert in Dallas Friday night when a fire broke out in a bank of lights above the stage.  The show began without any problems, but had to be cut short when a fir broke out in the rafters above the stage just as Rihanna was finishing "California King Bed".  The singer was lowered below the stage on a riser after the song and evacuated from the arena. Firefighters were called to the scene, but American Airlines Center employees had apparently extinguished the blaze by the time they arrived.  No official word yet on a cause, but witnesses say they believe the fire was started by pyrotechnics used during the show.  Watch footage of the blaze, and fans reaaction to the fire being put out, below.  No makeup date has been announced, but Rihanna later tweeted:  "DALLAS!!! We set the stage on FYAH tonight!!! LITERALLY!!! I'm so pissed, I was havin so much fun wit yall too!!! I gotta come back man!!"