As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING APU START, GROUND CREW REPORTED FIRE COMING FROM APU. DOWN POWERED THE ACFT AND ON EXITING SAW ONLY SMOKE COMING FROM THE TAIL. INSPECTED THE APU BAY FOR SIGNS OF FIRE DAMAGE, NO DEFECTS NOTED. APU WILL NOT START. GROUND RAN APU MULTIPLE TIMES. ALL APU PERAMETERS NORMAL. NO DEFECTS NOTED. OK FOR SERVICE.