As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
CLIMBING THROUGH 12000 FEET, THE MASTER WARNING AND SMOKE LIGHTS ILLUMINATED. AFT EXTINGUISH LIGHT WAS PUSHED AND AFT BOTTLE LOW LIGHT ILLUMINATED. SMOKE WARNING REMAINED ILLUMINATED. DISCHARGED FIRE BOTTLES AND RETURNED TO FIELD. LANDING UNEVENTFUL. AIRCRAFT REMOVED FROM SERVICE. INSPECTION OF AFT CARGO BAY REVEALED NO EVIDENCE OF FIRE OR SMOKE. REPLACED BOTH AFT CARGO BAY SMOKE DETECTORS IAW AMM 26-12-01-000-801, AND 26-12-01-400-801, PARA 1-4. RETURNED TO SERVICE.