L'Alpe d'Huez (France) (AFP) - Former champion Vincenzo Nibali was forced out of the Tour de France on Thursday after fracturing his back in a collision during a drama-packed 12th stage to the summit of Alpe d'Huez, his Bahrain team doctor confirmed.
Nibali, who claimed his sole yellow jersey in 2014, was transported to hospital with a suspected vertebra fracture after coming down hard around 4km from the summit of the legendary Tour climb.
Early reports, later backed up by Nibali, claimed he had collided with a police motorcycle.
However a video which emerged hours after the stage finish, shown on the website gazzetta.it, suggested a bag strap, flag or arm got in Nibali's way as he negotiated his way, shrouded in yellow smoke from rocket flares being set off, through a throng of hyper-excited fans.
Bahrain confirmed he had fractured the "tenth vertebra in his back" and would not start Friday's 13th stage from Bourg d'Oisans to Valence because of "difficulty breathing".
Nibali later confirmed his departure in a message to fans on his Twitter page.
"Hi guys, I've returned to the hotel but unfortunately the outcome of the medical report isn't good," he said.
"They confirmed I've fractured one of the verterbrae, so tomorrow (Friday) I head home to begin my recovery.
"Thanks for all the affection you've shown me. See you soon!"
Despite being helped back on his bike, and valiantly finishing only 13secs behind stage winner Geraint Thomas of Team Sky, the crash ended Nibali's bid to stay in contention on the race, which he leaves after climbing to fourth overall at 2:37 behind the British race leader.
Before being taken to hospital in Grenoble, the Italian appeared to blame a police motorbike.
"As the road narrowed, there were two police motorbikes closeby," he said.
"(Chris) Froome accelerated, I followed him. Suddenly, it slowed down in front of me, and I hit the deck.
"I was feeling good, I really believed in my chances. It's a pity. But these kinds of things can happen when there's a lot of people on the road."