Philippine Air Lines flight PR512, an Airbus A330-301, departed Singapore-Changi International Airport at 20:13 hours local time, with destination Manila, Philippines. On board were 11 crew members and 203 passengers. The aircraft landed at Manila about 23:00 following an uneventful flight. The aircraft parked at Bay 43 of Terminal 2 at 23:05 hours. The doors were opened and the flight crew allowed passengers to deplane and cargo to be offloaded. At about 23:25 when the checklist for securing and parking the aircraft was completed, the Electronic Centralized Aircraft Monitor (ECAM) warning indicated smoke in the aft cargo hold. Then, the rear cabin crew heard crackling sounds and later noticed smoke coming from the rear of the cabin. One of the rear cabin crew rushed to the cockpit and personally relayed to the captain that there was smoke in the rear of the cabin. At this point, the captain with the FO went out of the cockpit and verified the smoke. The captain went back to the cockpit alone, and discharged the fire extinguishing bottles for the aft cargo compartment and then went out of cockpit. After a while, upon remembering that the battery was already off, the captain returned to the cockpit, put on the battery and repeated the firing of the fire extinguishing bottles for the aft cargo compartment. After this, at about 23:55 the captain departed the aircraft since the cause and source of the smoke was undetermined. When the aft cargo door was opened there was thick smoke and hot air pushing out. The cargo loader immediately moved away from the aft cargo door and returned to close the door. Fire services attended to suppress the fire and smoke. Then the cargo loaders unloaded the Unit Loading Devices (ULDs) that were affected by fire. Initial investigation conducted showed that out of six ULDs in the aft cargo compartment for baggages and cargoes, there were four ULDs affected by the fire. The aft cargo compartment showed substantial damage by fire. PROBABLE CAUSE The Aircraft Accident Investigation and Inquiry Board determined that the probable causes of this accident are the following: – The inadvertent mixing of dangerous substances glycerin and potassium permanganate initiated the incipient fire in aft cargo compartment. The incipient fire at the aircraft Aft Cargo Compartment was triggered by inadvertent mixture of spilled contents of individual small containers of dangerous substances containing potassium permanganate and glycerin contained in luggages of passengers who were Kayak athletes placed at aft cargo compartment. Contributory Factor: – Inadequate system of identifying contents of checked-in passengers’ baggages that contain dangerous goods. The check-in baggages contain amounts of dangerous goods and other chemicals that when inadvertently spilled and made contact with each other will initiate fire. These dangerous goods in small quantities were not adequately covered by manual/psychological and technology inspection/monitoring at the aircraft point-oforigin and when not well-secured in luggages provide the probability of inadvertently mixing while on flight. – Inadequate proficiency of pilot in the timely implementation of the procedures for Aft Cargo Compartment Smoke Warning. The PIC upon indication of smoke warning after aircraft “on block” failed to immediately execute Level 3 procedure which include triggering of fire extinguishing bottles and call out for support from airport fire fighting capabilities. Underlying Factor: – Inadequate passenger information and airport security procedure on the identification and control of the updated list of dangerous goods and its safety handling. The passengers are under informed on the safety aspects of handling or avoiding transport of dangerous goods. Likewise, airport security personnel still need dynamic update in training and equipage to closely inspect/monitor its transport by air.