The death toll on Mountt Everest has risen to 4 with the discovery of the climbers' bodies, while one still remains missing. The fatalities happened on the descent and it seems they could have been caused by a backlog of people struggling to reach the summit. As many as 150 people were waiting to leave Base Camp and some were still making the final ascent at 2.30 when safety guidlines stress that the latest departure time is 11.00. The congestion meant that there was a long delay with longer exposure to high altitude. In turn this is likely to have increased health risks with climbers running out of limited reserves of oxygen.