Ralf Schumacher has been cleared of making an error that led to the massive accident he suffered on the opening day of the latest Formula One group test at Monza.

The German reportedly somersaulted his FW25-BMW after running off the road at 150mph while negotiating the Lesmo curves at the far point of the Italian circuit, and was taken to hospital for checks after being extricated from what remained of the car.

The team instantly promised a full investigation into the incident, and has since revealed that it was most likely the result of a mechanical failure. Driver error on Schumacher's part has been excluded from the possible causes.

"The team is currently investigating the cause of the accident, but has ruled out driver error," said a statement issued on the team's website.

Chief operations engineer Sam Michael admitted to Britain's Daily Telegraph newspaper that the team was 'not 100 per cent sure what happened, but it was some sort of technical failure'. He added that, remarkably, the car wasn't a write-off, and was already on its way back to Grove to be repaired.

Despite hospital policy requiring any admissions to be detained for a full 24 hours for observation, Schumacher yesterday discharged himself and returned to his private clinic in Austria, while test driver Marc Gene was drafted in to cover his duties at the track.