Security camera footage in the Sierre-Sion tunnel as well as the skid marks on the road have helped establish the coach’s deadly trajectory.
Shortly after entering it slammed into the wall of the tunnel and came to rest in a mangled heap at the end of a lay-by.
Belgium’s Prime Minister, Elio Di Rupo paid tribute to the emergency workers saying many were left traumatised by having to deal with the aftermath.
But he added there was no way to describe the pain relatives of the victims must be feeling: “There aren’t any words because the pain is so personal and so intense. We’d like to ease it in some way, but when we lose a child or have one suffering, there are no words. It is important to console their families,” said Di Rupo.
Initial investigations have been able to determine other key elements crucial to what may have happened. Conditions were good, the coach appeared not to be speeding and no other vehicle was involved. Most of the passengers were wearing safety belts, but the impact of the crash may have rendered them useless.
Valais state prosecutor, Olivier Elsig, said they are now working on three main theories. The first is that there may have been some sort of technical problem with the coach, although it was fairly new and recently serviced.
Secondly, the driver may have been ill or suffered some sort of malaise. This, Elsig said, will be determined by the results of an autopsy. Thirdly, the crash may have been the result of human error.