As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
FOUND SMOKE DETECTOR LOOP LIGHT ON IN FLIGHT, FORWARD CARGO COMPARTMENT LOOP-B. CREW REPORTED LOWER CARGO COMPARTMENT SMOKE DETECTION SYSTEM DID NOT TEST AFTER B-LOOP LIGHT ILLUMINATED. INSPECTED FORWARD AND AFT CARGO COMPARTMENT, NO DEFECTES NOTED. CHECKED CONTROL PANEL, ALL NORMAL ON GROUND. ASSIGNED TO MEL. FURTHER TROUBLESHOOTING REQUIRED. REMOVED AND REPLACED FAULT PANEL ASSEMBLY IAW DC9 MM 26-10.