As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ON DEPARTURE, FUSELAGE DOOR WARNING LIGHT ILLUMINATED. VERIFIED AFT CARGO DOOR OPEN INDICATED ON DOOR PAGE. ACFT NOT PRESSURIZING. DECLARED EMERGENCY AND RETURNED TO FIELD. LANDING UNEVENTFUL. REMOVED FROM SERVICE. INSPECTED, FOUND THE AFT CARGO DOOR HANDLE POPPED, INSPECTED, PERFORMED OPS TEST IAW AMM 52-31-00-710-801. OPS TESTED GOOD, NO DEFECTS NOTED. RETURNED TO SERVICE.