The granite tower, home of several classic routes such as The American Direct, released approximately 12,000 cubic metres of rock in a series of three large collapses according to the local Chamonix newspaper.
Chamonix valley resident Bobby Drury was in the air above the mountain with his paraglider just after the time of the first rockfall:
"The first fall was around 1pm on Saturday. I'd been watching the clouds start to form on the Flames de Pierres with a view to going flying that afternoon. Then I noticed that a strange cumulus-looking cloud had formed that was the height of the pillar. It was in the wrong place for a cumulus at that time of day so I guessed it was a rockfall. I went up there that afternoon and soared up the Dru to check it out. There was a lot of dust on the lower ledges so I knew it'd been a rock fall. There were two parties on the upper pitches who much have just missed it!"
Bobby was also well positioned in the valley to watch Sunday's larger collapses:
"Sunday was the bigger falls. The first was a monster, about 10am. Andy Parkin was next to me and reckoned it was a big as the one that took the Bonatti Pillar away a few years back. It filled the valley with a cloud of dust. Then three more falls occurred between midday and 1pm. Then the weather closed in so not sure if there's been any more."
The Dru suffered a previous major rockfall back in 2005, when a much larger collapse occurred destroying several routes including The American Directissima (Not the American Direct - don't get them confused!).
Professional Mountain Guide Andy Perkins commented on his blog:
"The first of 3 rockfalls in 2011 occurred on the afternoon of Saturday 10th September, with 2 more taking place on Sunday 11th September. These appeared to be on the west and north face of this iconic mountain.
There are some great photos on Rob Jarvis' blog, as he had the good fortune to be on the Aiguilles Rouges at the time and a quick camera reflex. Houses in Les Tines were coated with granite dust as a cloud spread over the valley.
No one was killed in the incident but a team was rescued from the American Direct (presumably needing clean underwear). The Office de Haute Montagne say the American Direct remains intact but they are advising complete avoidance of the Dru, even the normal route, until the end of the summer season."
- More info - Andy's Blog
Thanks go to Bobby Drury for the photos that accompany this report.