A group of experts appointed by the canton of Graubünden delivered their findings on Friday, news agencies reported.
They told the media a very rare chain of events led to the collapse of one side of the Piz Cengalo mountain and the resulting landslide.
Three million cubic metres of rock, the volume of 3,000 houses, collapsed on to the glacier dislodging within seconds a huge amount of ice that was then pulverized or melted.
The melted ice then sent a wave of mud, rock and debris crashing into the Bondasca valley below, according to the 20-strong expert team set up to look into the causes of the disaster.
They warned that further rockfalls are likely as more than one million cubic metres of rock is still in motion.
Heavy rainfall could result in further landslides in the coming years.
No inhabitants of Bondo were injured in the disaster of August 23rd, but eight people hiking in the area were reported missing.
More than one hundred people had to be evacuated and several buildings were destroyed.
It was two months before most of the evacuated could return home.
Bondo residents have been told that reconstructing the village could take years.