BE 400XP CARGO DOOR OPENED IN FLIGHT DURING TURBULENCE ENCOUNTER; AND CONTENTS DEPARTED ACFT.

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ACFT WAS SERVICED WITH FUEL AT LMT. AT THE TIME OF REMOVAL OF PAX BAGS; THE REAR BAGGAGE DOOR WAS CLOSED; LATCHED AND LOCKED. UPON COMPLETION OF SVC AND PRIOR TO ENGINE START A VISUAL INSPECTION WAS PERFORMED WITH NO ABNORMALITIES NOTED. COMMENCED REPOSITION (FERRY) FLT. STARTED ENGINES USING CHECKLIST AND COMPANY PROCS AND TAXIED FOR DEP. NO ANNUNCIATOR INDICATIONS. DEP; TAKEOFF AND CLIMB WERE ALL NORMAL AND THE ANNUNCIATOR PANEL AND MASTER CAUTION WERE CLEAR. DURING CLIMB; AT APPROXIMATELY 11500 FT MSL WE ENCOUNTERED MODERATE PRECIPITATION AND LIGHT TO MODERATE TURBULENCE. AT THAT TIME THE 'DOOR UNLOCKED' ANNUNCIATOR ILLUMINATED ALONG WITH THE MASTER WARNING FLASHER. NO VIBRATIONS OR OTHER ABNORMALITIES WERE FELT INSIDE OF THE ACFT. MY FO (WHO WAS PF) SLOWED THE ACFT WHILE I NOTIFIED ATC OF OUR INTENTION TO RETURN TO THE ARPT. WE WERE VECTORED TO RETURN TO THE ARPT. WE LANDED NORMALLY AND TAXIED TO THE RAMP. NO VIBRATIONS WERE FELT OR HEARD ON DESCENT OR IN THE LNDG CONFIGURATION. UPON EXITING FROM THE AIRPLANE I NOTICED THAT BOTH BAGGAGE DOORS WERE OPEN. NO DAMAGE WAS NOTED TO THE ACFT. MY BAG AND THE ENGINE COVERS BAG HAD EXITED THE ACFT. I BELIEVE THE EVENT WAS CAUSED BY THE BAGGAGE DOORS PARTIALLY OPENING IN FLT DUE TO TURBULENCE. NO INDICATION OF A DOOR OPEN WAS EVER SEEN ON THE GROUND OR DURING CLIMB. ALSO; A VISUAL INSPECTION NOTED NOTHING ABNORMAL. SEVERAL GND PERSONNEL SERVICED THE ACFT (GPU REMOVAL) AND WITNESSED OUR TAXI OUT. I BELIEVE THAT THE LOSS OF EQUIPMENT COULD HAVE BEEN PREVENTED BY HAVING A CARGO NET INSTALLED OVER THE OPENING OF THE BAGGAGE DOOR.CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR STATED THAT THE BAGGAGE ACCESS CONSISTS OF TWO DOORS -- A SMALLER DOOR WHICH IS HINGED AT THE TOP WITH PINS SECURING THE DOOR ON BOTH SIDES. A LATCH ACCESSIBLE FROM BOTH INSIDE AND OUTSIDE DRIVES THESE PINS TO THE LATCHED POSITION. THE LARGER BOTTOM DOOR OPENS DOWNWARD AND ITS LATCH MECHANISM SECURES THE DOOR TO THE UPPER DOOR WITH TWO LATCHES. IT IS SPECULATED THAT PERHAPS DURING THE TURBULENCE; ONE OF THE CREW SUITCASES MAY HAVE COME INTO CONTACT WITH THE UPPER LATCH; ROTATING IT SUFFICIENTLY TO ALLOW IT TO OPEN.