As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
CREW REPORTED, APU FIRE INDICATION DURING CRUISE. A-LOOP OF FIRE DETECT SYS SELECTED 'B', NO FURTHER INDICATIONS. APU WAS OFF DURING THE ENTIRE EVENT. DEF ITEM PER 26-7, MMOC J SHULTZ ASSIGNED CTRL. NR M-108335, PLACARD A-LOOP SYS INOP AND SELECTED 'B' LOOP.