Michael Schumacher remains in a "critical but stable" condition, his spokeswoman said, as French investigators hoped a helmet-mounted camera he was wearing at the moment of his ski accident could provide answers.
It was not known whether the GoPro camera filmed the moment when the retired seven-time world champion slammed his head against a rock, or whether images have been damaged by the impact, which was so hard it split the helmet he was wearing.
But investigators may yet find another clue in a film made by a German witness, who claimed to have captured Schumacher's accident by chance, German news magazine Der Spiegel reported late Saturday.
The magazine quoted the witness describing Schumacher descending the slope at a "leisurely" pace and "at a maximum speed of 20 kilometres an hour".
In the background, a skier could be seen descending on an unmarked run between two groomed pistes before falling, the magazine reported.
Key among elements that investigators are hoping to establish is the speed at which Schumacher was skiing, as it could determine responsibility in the December 29 accident in the French Alps near the Meribel ski resort.
French prosecutors and the ski resort say Schumacher was skiing at great speed. His spokeswoman Sabine Kehm has challenged that, saying he could not have been going fast "because it appears he helped a friend who had just fallen".
Edouard Bourgin, a specialist on accident claims said: "There could have been a catapult effect that explains the violence of the shock, even in the absence of excessive speed."
Prosecutors are also looking at whether the limits of the ski runs next to the accident site were correctly marked and whether the rock in question was lying close enough to the piste to require some kind of protection or signage.
In addition, they are examining whether the safety releases on Schumacher's skis operated properly.
"I don't think it's normal that between two marked slopes there would be this passage with rocks showing that is not fenced off," said Philippe Streiff, a former French racing driver, in the French sports daily L'Equipe.
A paraplegic since an accident in Rio de Janeiro, Streiff visited the Grenoble hospital on Friday to hand a message to Schumacher's wife Corinna. Other family members at his bedside include his two teenage children, his father Rolf and brother Ralph, who is also a racing driver.
Schumacher turned 45 on Friday, and fans marked the birthday with a silent vigil outside the