A B747 IN CRUISE AT FL250 EXPERIENCED A GALLEY OVEN FIRE EXTINGUISHED WITH 2 HALON BOTTLES CAUSED BY DEBRIS COLLECTING ON THE TOP SURFACE OF THE OVEN LINER.

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THIS WAS A SCHEDULED ACR FLT; ACR XYZ; FROM SHANGHAI TO TOKYO. ACFT WAS A B747-200 IN PAX CONFIGN. DURING CRUISE THE CHIEF PURSER RPTED HE WAS FIGHTING A GALLEY FIRE IN THE FORWARD GALLEY OVEN. WE INITIATED THE EMER COCKPIT PROC WHICH PRIMARILY INVOLVED DISCONNECTING ELECTRICAL PWR TO THE GALLEYS. THE SO THEN PROCEEDED TO THE GALLEY AREA TO SUPPORT THE FIRE FIGHTING EFFORTS. UPON HIS ARR THE FIRE WAS EXTINGUISHED AND HE VERIFIED THAT IT HAD BEEN CONTAINED ENTIRELY TO THE INTERIOR OF 1 OVEN. THIS OVEN WAS UNLOADED AND FURTHER INSPECTED FOR RESIDUAL HEAT AND ANY POTENTIAL FOR FURTHER IGNITION. HE THEN RPTED BACK TO ME THAT THE SIT WAS UNDER CTL AND STABLE. I THEN INSPECTED THE GALLEY PERSONALLY AND VERIFIED THAT THERE WAS NO ONGOING HAZARD TO THE ACFT; PAX OR CREW. THE CREW UNIVERSALLY FELT THAT NO FURTHER EMER PROCS WERE REQUIRED AND POTENTIAL HAZARDS WERE NOT OCCURRING. NOTIFICATION WAS MADE TO THE AIRLINE MAINT CTR IN ZZZ AND TO THE STATION OPS STAFF IN TOKYO WHERE A NORMAL LNDG WAS MADE. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED THAT AFTER THE PURSER DISCHARGED THE FIRE BOTTLES AND EXTINGUISHED THE FIRE THE RPTR INSPECTED THE OVEN AND COULD FIND NO SOURCE OF THE FIRE NOR ANYTHING BURNED. THE RPTR SAID THE DECISION WAS MADE TO CONTINUE ON TO THE FLT DEST. THE RPTR STATED LATER ON AFTER THE OVEN HAD BEEN REMOVED AND SENT TO THE SHOP IT WAS DISCOVERED PLASTIC AND FOOD DEBRIS WAS THE CAUSE OF THE FIRE. THE RPTR SAID THE MATERIAL WAS EITHER LEFT ON TOP OF THE OVEN LINER WHEN LOADED OR PULLED OUT OF THE LINER BY THE OVEN FAN LOCATED IN THE OVEN TOP SURFACE. THE RPTR STATED THAT NONE OF THE CREW WAS AWARE OF THE REMOVABLE OVEN LINER AND NOT SEEING ANYTHING COMBUSTIBLE INSIDE THE OVEN COULD LEAD TO A BAD DECISION. THE RPTR SAID CREWS SHOULD BE MADE AWARE OF THIS REMOVABLE LINER SO A COMPLETE INSPECTION CAN BE ACCOMPLISHED.