The collapse was material blocking a raise/winze between the Upper stope and middle adit. It's swept down and into the main shaft, choking high up (looking as far as one can up from the drainage adit, there's nothing to be seen). From recollections of within the upper stope and what's not there now, a significant amount of material has relocated. So who knows how thick the shaft choke is. There's surprisingly little at the base so when 'it' eventually goes, don't be standing anywhere near.
Some comparative photos.
Before...
[photo]51991[/photo]
After...
[photo]121069[/photo]
And this :o:)
[photo]63666[/photo]