Mercedes have launched an investigation into the cause of Michael Schumacher's accident at the start of Saturday's qualifying session for the Belgian Grand Prix.
The initial 20-minute run was just 90 seconds old when seven-times champion Schumacher, on the weekend when he is celebrating the 20th anniversary of his Formula One debut, crashed out.
Inexplicably, the right-rear wheel detached itself from the car, sending Schumacher into a wall, the 42-year-old sliding down the hill into a gravel trap at Rivage on three wheels.
Initially, Schumacher believed himself to be at fault, only to later discover that was far from the case, despite the incident leaving the German starting his favourite race at the back of the grid.
Team principal Ross Brawn said: "I'm disappointed for Michael because the conditions would have suited him perfectly.
"We need to look at exactly what happened, but it would appear there was something amiss with the right-rear wheel attachment.
"We need to go through it carefully tonight to ensure there can be no repeat."