Four carriage horses are understood to have crashed into a clothes shop window in Ascot.
Locals reported the "horrendous" horse and carriage incident near to the High Street, just a short walk away from the racecourse.
Several people were thrown from the carriage and two of the horses smashed into the glass window, a witness claimed online.
A section of the window of Nataliya Couture was completely shattered with glass lying around the displays and a shutter at the back of the space buckled.
A policeman at the scene told Press Association that he understood the incident involved four horses.
One horse looked particularly injured, a taxi driver who saw it happen said.
Gary Copeland tweeted shortly after the incident at around 6.15pm, saying he had witnessed an "awful accident".
"One of the large horse carriages bolted down the High Street right in front of me," he wrote.
Mr Copeland said the carriage "careered over a roundabout and through a shop window".
He added: "I saw several people thrown off, and two of the horses were jammed in the window, it looked like one was down in its side.
"It didn't look good at all. The driver was going so fast, at the roundabout one horse just slipped over and that was it then, carnage. Awful."
Another witness, Lucy Fowler, told the Standard she saw the horse and carriage movely "very quickly" down the road before it "quickly braked".
"It then looked like one of the horses legs buckled as the carriage went narrowly over the roundabout and then it crashed."
She added that "there was a lot of glass and shocked faces".
The shop was closed when the incident took place.