A secondary tunnel was then drilled for safety reasons. A week later the level of the lake reached 10 metres below the tunnel. On 27 May an enormous piece of ice detached itself from the cone in the lake and floated to the surface while making terrible noise; everybody escaped. They went back to work two days later. The 198 metre-long hole was completed on 4 June. Other large pieces of ice detached from the cone and floated back. The waters finally reached the level of the hole on 13 June, 22:00. They continued to rise until 14 June, when the level of the lake began to fall because of the erosion of the hole by the waterfall. Some water also ran out from the base of the cone. Only two men stayed in place; Venetz warned the inhabitants of the valley of the danger. On the morning of 16 June, terrible noises and violent detonations were heard. The cone began to crack. A group of British tourists and a drawer from Lausanne visited the place with Venetz. In the afternoon, Venetz and the workers escaped to the heights of Fionnay. Finally, at 16:30, the dam broke and 18 million m3 of water invaded the valley. Half an hour later the lake was empty. The flood reached the village of Bagnes 10 minutes later; the alert was given to Martigny before 18:00, but too late. The wave invaded Martigny-Bourg a few minutes later. The rise of the waters was observed along the Rhone, at 19:00 in Saint-Maurice and at 23:00 on Lake Geneva.