What was found
DURING TAKE OFF, HAD TO ABORT AT 70-80 KTS DUE TO FUESLAGE DOOR WARNING LIGHT COMING ON. AFT BAGGAGE DOOR LIGHT WAS INDICATING OPEN. AIRCRAFT REMOVED FROM SERVICE. GVI OF AFT BAGGAGE DOOR IAW Q400 AMM 05-48-13-941-001. NO DEFECTS NOTED WITH EXTERNAL AREA OF AFT BAGGAGE DOOR. OPS TEST OF AFT BAGGAGE DOOR IAW Q400 AMM 52-31-00-710-801. OPS TEST GOOD. DOOR CLOSES AND ALL INDICATIONS SHOW DOOR CLOSED / LOCKED. NOTE: UPON AIRCRAFT ARRIVAL AT GATE, NOTICED AFT BAGGAGE DOOR HANDLE WAS POPPED OUT OF RECESS.COULD NOT DUPLICATE. RETURNED TO SERVICE. NO PARTS REPLACED.