Michael Schumacher did not reduce his speed significantly after going off-piste prior to his accident, French prosecutors said.
The investigators said the Formula One champion tried to reduce his speed, before one of his skis hit a rock, causing Mr Schumacher to fall.
The investigator added that Mr Schumacher was following the rules imposed in the French resort.
The racing driver, who suffered a severe head injury while skiing off-piste in the resort of Meribel in France last Sunday, remains in an artificially induced coma.
More top news
Known as 'spice' and 'black mamba', the so-called legal high is suspected of contributing to deaths in male and female institutions.