There was a grisly end to Ladies’ Day at Royal Ascot when a horse-drawn carriage careered out of control across a roundabout and two of the horses pulling it smashed through the window of a clothes shop on Ascot high street.

It was feared that one of the horses had suffered fatal injuries in the incident, witnessed by many of the 70,000-strong crowd as they left the Queen’s track.

Mohamad Amjad, a 47-year-old taxi driver, said he thought the accident was caused by one of the horses becoming “panicked” and setting off at a run down the road. Marks across the kerb showed where the two lead horses had then scrabbled to keep their footing before hitting the window.

Such carriages are available for private hire by racegoers who want to arrive in traditional style at the track and have become one of the enjoyable sights of Royal Ascot as they trot between the grandstands and nearby car parks, some passengers seated on top and others inside. It is believed most of the passengers aboard the runaway carriage were unharmed, while one was treated for minor injuries at the scene.

“The horses started running very fast and they lost control,” Amjad said. “One was injured very badly. Someone put a towel on it, to try to control the blood.” He described the horse as lying on its side on the pavement, bleeding profusely from a long wound in its side.

The injured animals were taken from the scene in a horse ambulance, while two others were said to be unharmed.

Witnesses shared their shock about what had happened in the incident on social media.

Gary Copeland said on Twitter: “One of the large horse carriages bolted down the high street right in front of me and careered over a roundabout and through a shop window. People thrown off and horses jammed in the glass window. Not nice to see.”

Lucy Fowler said she had been approaching the roundabout in her car and had to brake suddenly when she saw the carriage coming down the hill at speed. “Awful to witness such a horrendous horse and carriage accident in Ascot – poor horses sped down the high street and smashed into a shop window with people on board. Just hope everyone is ok.”