And a rare lightning storm last month provided an enthusiastic source of ignition for fires.

上个月一场罕见的闪电风暴为火灾提供了火源。

Mysteriously, no source of ignition could be found for the blaze, and the flames had not spread to the rest of the room.

奇怪的是，找不到引起大火的火源，火焰也没有蔓延到房间的其他地方。

The most likely explanation is an external source of ignition — a match, a cigarette, an electrical spark, the evidence of which is destroyed by the blaze.

最有可能的解释是外部引火源——火柴、香烟、电火花，这些证据都被大火烧毁了。