American favourite Chloe Dygert suffered a terrible crash in the time trial at the UCI Road World Championships on Thursday.
Dygert was setting the pace again after winning last year's title and looked on course for gold on the 31.7km circuit at Imola, but lost control on a corner.
The 23-year-old hit a barrier and tumbled over the top down a bank. Her team car immediately came to her aid.
Images showed Dygert with blood across her legs and paramedics were soon in attendance as she was taken into a ambulance.
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Her coach, three-time Olympic gold medallist Kristin Armstrong, confirmed to Cyclingnews that Dygert had suffered a severe laceration.
"Currently we don't know the prognosis yet. I know for a fact that she was flown to a hospital in Bologna and that she is being seen by doctors in the emergency room now," she said.
"They were all concerned with a deep laceration to her leg, where she hit that guard rail, it's horrifying and sickening, and it's going to be a hard recovery for Chloe.
"This is definitely a serious accident but she will look back on it and hopefully be able to say that she was lucky in a lot of ways. It could have been more serious."
USA Cycling had earlier tweeted: "All we know is that she is conscious and talking. More updates to come."
With additional reporting from Reuters