Michael Schumacher remains in a "critical but stable" condition, his spokeswoman said on Saturday, 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 on Saturday.