Children were thrown from an inflatable slide when it was blown through the air at a car boot sale.
Up to six people were taken to hospital after the slide was sent careering through stalls, landing upside down against a vehicle at Ripley Cricket Club, near Harrogate, North Yorkshire, it was reported.
Several youngsters were on the slide at the time and bounced off before it was carried through the air, the Daily Mail said.
Leanne Forde, 24, a veterinary surgeon, told the newspaper: "I couldn't believe what I was seeing. All of a sudden the slide blew over and was being blown across the field. It was really busy and there were people trying to run out of its path. I could hear people screaming and stalls were being knocked over.
"There were kids playing on the slide at the time. The slide was really high so if a child had been standing at the top when it blew over I dread to think what could have happened. It only stopped blowing across the field when it got stuck against a vehicle."
Police were alerted to the incident at 11.10am on Sunday by the ambulance service.
Five of the injured were taken to Harrogate District Hospital and another person was taken to Leeds General Infirmary, suffering from chest pains.
It is not believed that anyone was critically injured.
A North Yorkshire Police spokesman said: "Officers have seized the slide and investigations are continuing at the scene.
"The Health and Safety Executive have been informed and are also attending the scene of the incident."