At least 28 spectators were injured when a 200-mile-per-hour crash involving several vehicles sent debris flying into the stands during a Nascar race in Daytona, US.
Officials said that 14 people needed hospital treatment following the incident on Saturday 23 February.
"It was freaky," fan Rick Harpster told the Associated Press news agency.
"I saw a tyre fly straight over the fence into the stands. I knew it was going to be severe."
Another eyewitness described people running, and seeing a girl completely covered in engine oil.
One injured man required surgery for a life-threatening head injury, while a 14-year-old boy was in critical but stable condition.
The crash came in the last lap of the second-tier race as the cars approached the chequered flag.
The race leader moved to the side to prevent another vehicle overtaking, and cars following behind collided, with one flying into the protective fence separating spectators from the track. A ten-car pile-up ensued.
The crash came on the eve of the Daytona 500, one of the most famous Nascar events, but organisers insisted that the event would go ahead.
Nascar's vice president of race operations, Steve O'Donnell, said that the fencing, which was ripped apart by flying debris, was being replaced and the incident would be reviewed.