What the Swiss authorities are able to tell us is what they think didn't cause the crash. They have very little idea of actually what did.
We know that the weather was good, that the road was dry, they are pretty sure that the coach was not speeding, the driver was well rested, this at the very beginning of what was going to be a long drive back to Belgium.
They might find clues in the wreckage as to exactly what did but it's perfectly possible that they may simply never know.
A nation grieves for the 28 victims of the coach crash in Switzerland as a military aircraft has carried the bodies home.
First pictures have been released of the young victims of the Swiss bus crash. They are on display for people to pay their condolences.
A British boy was among the 28 people killed in a horrific bus crash in a Swiss tunnel.