British Indy Car drive Dan Wheldon has been airlifted to hospital after a 15-car pile-up in Las Vegas.
The 33-year-old is said to be in a critical condition after the crash on Lap 12.
"I've never seen such a mess in my entire career on the race track," said driver Danica Patrick. "It was like a movie scene, it was as if they were trying to make it look as gnarly as possible.
"It was debris everywhere across the whole track, you could smell the smoke, you could see there was a chunk of fire we were driving around out there."
Wheldon had been in line to win $5m top prize had he won the race.
"I'll tell you, I've never seen anything like it," said Ryan Briscoe. "The debris we all had to drive through the lap later, it looked like a war scene from Terminator or something.
"I mean, there were just pieces of metal and car on fire in the middle of the track with no car attached to it and just debris everywhere. So it was scary, and your first thoughts are hoping that no-one is hurt because there's just stuff everywhere. Crazy."
Scotland's Dario Franchitti was crowned champion after the crash.