What was found
D: DURING PRE FLIGHT SET UP AT GATE WE HEARD A LOUD POP AND THEN GRINDING NOISE COMING FROM RIGHT SIDE OF AIRCRAFT BEHIND CARGO DOOR. FO SAW BLACK SMOKE COMING OUT OF VENT BEHIND A CARGO DOOR. SMOKE STARTED FILLING THE COCKPIT AND CABIN AND IMMEDIATELY SHUT DOWN A/C. / C: MEL 21-51-0D / CAT: C DUE DATE: 09 NOV 2021 / ***ODI EVENT*** SMOD APPROVAL REQUIRED PRIOR TO RTS*** / DURING PRE FLIGHT SET UP AT GATE WE HEARD A LOUD POP AND THEN GRINDING NOISE COMING FROM RIGHT SIDE OF AIRCRAFT BEHIND CARGO DOOR. FO SAW BLACK SMOKE COMING OUT OF VENT BEHIND A CARGO DOOR. SMOKE STARTED FILLING THE COCKPIT AND CABIN AND IMMEDIATELY SHUT DOWN A/C. (FLIGHT 5505 - FILED CLOSED) / OCT 31, 2021 STATION: SDF--PERFORMED TROUBLESHOOTING ON EAML LOG 769180, DEFERRED BOTH PACKS PER MEL 21-51-0D, NO MX ACTION REQUIRED. PLACARD INSTALLED