Initial reports that it was a "gas explosion" were false.
One fatality has been reported but he appears to have been the attacker.
Apparently, he targeted a wine bar after being denied entrance to the cancelled festival.
From Deutsche Welle (7:15 PM CST)
Blast caused by explosive device kills one person near Nuremberg
Police in the town of Ansbach near Nuremberg have said a man was killed when an explosive device he was believed to be carrying detonated near an open-air music festival. Eleven other people were injured.
Bavaria's Interior Ministry has confirmed that the explosion on Sunday night appears to have been intentional.
The blast occurred shortly after 10 p.m. local time.
Police said in a statement that "a man, according to our current knowledge the perpetrator, died" in the blast.
Bavaria's Interior Minister Joachim Herrmann is on his way to the town.
NTV television reported that the music festival being held nearby had been canceled for the evening. There were 2,500 people attending the event.
Ansbach Mayor Carda Seidel said the explosion was near to an entrance of the festival.