Sir Dave Brailsford, the Team Ineos principal, said that Froome's front wheel had been caught by a gust of wind while he took one hand off the bars to blow his nose.
Team Ineos officials have not confirmed Froome's condition, but the French sports daily L'Equipe is reporting that Froome may have suffered a fractured femur.
Britain's four-times victor of the Yellow Jersey was airlifted to hospital with multiple injuries - including a broken leg, broken elbow and fractured ribs - after a crash that shook cycling. He has also suffered fractured ribs.
Ineos principal Dave Brailsford confirmed to French television that the four-time victor will not start the Tour next month following a harrowing, high-speed crash during a training ride ahead of the fourth stage at the Critérium du Dauphiné.
Froome would have been trying to join the elite group of cyclists who have won the sport's greatest race five times, but now faces a long spell off the bike as he recovers from what is believed to be a broken leg. He is now being airlifted to St Etienne University Hospital for further treatment.
Seeking a fourth win in the key preparation race, Froome was eighth in the Dauphine standings, 24 seconds behind leader Dylan Teuns of Belgium.
Froome's injuries, which will nearly certainly rule him out of the world championships in Yorkshire in September, stunned Tour de France organisers.
The 34-year-old was using the race in Roanne, France, as part of his build-up to the Tour, which starts on 6 July.