I was just driving down Penge High street and had to turn back because there's a building on fire and they blocked the traffic off. Looks like near where the Queen Adelaide is but I could be wrong. From where I was I saw flames come out of the top of the building and fire engines were putting it out.
I heard there was a gas explosion in that area, could be what you saw. No mention on the BBC website, surprising since it was such a slow news day they had the devestating 'earthquake' as top story for most of the day.