What was found
(CAN) AT 5000 FT CLIMBING WE RECEIVED "FUSELAGE DOOR" WARNING. CHECK ON MFD SYS P. DOORS INDICATED THAT AFT CARGO DOOR UNSAFE. PERFORMED NORMAL & ABNORMAL CHECKLISTS & THEN RETURNED UNEVENTFULLY. DOOR WARNING REMAINED ON ALL WAY IN TO PARKING STAND. CREW & PASSENGERS DEBRIEFED AS NORMAL. VISUAL INSP OF CARGO DOOR AFTER LDG DID NOT REVEAL ANY EXTERIOR MALFS. MAINT INESTIGATION REVEALED CARGO DOOR CLOSED SWITCH FOUND STUCK. SWITCH LUBRICATEDAND SYS TESTED W/O FURTHER REMARKS. A/C RETURNED TO SERVICE.