In this photo, released by Neal Beidleman in 2011, unidentified mountaineers are seen walk past the Hillary Step while pushing for the summit of Everest. More than 50 climbers reached the top of Mount... more 

In this photo, released by Neal Beidleman in 2011, unidentified mountaineers are seen walk past the Hillary Step while pushing for the summit of Everest. More than 50 climbers reached the top of Mount Everest Friday at the start of a two-day window that has raised fears of perilous overcrowding on the world's highest peak after four deaths last week less