A report on the evening NHK News program showed the lastest report made by the Japanese Accident Investigators.
A rupture of 2-3 cm in size in the wing fuel tank was found that had been caused by a bolt lodged in the slat mechanism, which is surrounded by part of the fuel tank. It now appears that as the slat was retracted after landing the bolt was pushed back and pierced the tank allowing fuel to escape.
The orgin of this loose bolt has not yet been determined.
Attention has now switched from the pylon fuel line theory to this newly identified cause.
To answer Zazoo's question, a previous reported stated that the aircraft arrived with 5 tons of fuel remaining.
PTH
I would like confirmation that this indeed came from the investigating team.
I've seen several secondary incidents of fuel tank penetrations of the size of a bolt head and none of them resulted in a ground pool fire. The rate of evaporation vs the rate of flow seems to lower the risk.
Just how large was the bolt suppose to be in this latest rumor?