What was found
CARGO DOOR UPR A, CTR A, AFT A, FWD A MESSAGES CAME ON AT FL330. RAN QRH AND LANDED NEAREST SUITABLE AIRPORT. EMERGENCY DECLARED. INSPECTED ALL CARGO DOORS AND FOUND ALL DOORS WERE CLOSED AND LOCKED IAW AMM 52-32-00-2, 52-34-00-2, 52-31-00-2, 52-33-00-2. NO DEFECTS NOTED. . REPLACED MSC IAW AMM 31-42-01-5. RETURN TO SERVICE TEST PASSED.