As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
FIRE INDICATION, WARNING AND FIRE BELL DURING CLIMB. PERFORMED "FIRE ENGINE 4" CHECKLIST PER QRH. FIRE EXTINGUISHED IMMEDIATELY AFTER DISCHARGE OF ONE BOTTLE(FOUND NR 4 PRSOV STUCK OPEN. REPLACED PRSOV AND PERFORMED PNEUMATIC HEALTH CHECK. ALL PNEUMATIC CHECKS SATISFACTORY.)