Eight children were "potentially serious" injured after an inflatable carnival slide fell on a fireworks display.
Woking Park was evacuated in Surrey as doctors treated the injured.
The Surrey police reported a major incident after "a lot of kids dropped off the slope" on Saturday at 19:30.
Patients were taken to all "major trauma centers" in London, flying with an aerial rescue.
The location is approx. At 20:00, he was evacuated to get the helicopter and "more crew" from the southwest coast rescue service (Secamb) to help the injured.
The police first described the case as a collapse of a helter skelter, but corrected their meaning by describing a giant inflatable slider.
Seacamb first said that he had entrusted six children but later confirmed that he was the eighth figure – although there was no official confirmation of their age or their terms.
The fireworks were abandoned shortly after the children were injured.
Oliver Trimble, an eyewitness told the BBC that the speakers of the event had come to evacuate soon before 20:00.
He said he saw the victims being treated by doctors, adding: "It was a very scary sight to see.
"This is one of Woking's biggest events of the year, thousands of people coming to the fireworks," he said.
Anna Neale's local musician said she plans to take her 10 and 6-year-old daughter after a fireworks giant slider.
"We saw all the blue light and saw the air ambulance arriving, all evacuated very well, everyone was astonished," said the 36-year-old.
Event Organizers Woking District Rotary Club Twitter: "We were all very shocked and sorry for the events of the party."
"We focus on dealing with injured children in emergency services.
"Our thoughts with children and their families at the moment," he added.
The park will remain closed on Sunday when the police investigate the cause of the incident.
Officials called on the eyewitnesses, or the video clips or photos they had with their contacts.
Andy Datson said: "A serious incident in the Woking fireworks tonight, the whole park evacuated and the event was broken, the slide seems to have collapsed and the kids are falling off."
In 23-year-old Guildford, Surrey, she said she had seen up to 40 children on her own.
He said he was watching the fireworks to his friends before he saw "flashing lights".
Joe Mercer, the secretary of the Showmen Guild, told the BBC: "This student has up-to-date test certificates and insurance documents, these are provided to the police, their members fully cooperate with the authorities, no arrest has been made."
He added, "The Showmen Guild's members exhibit equipment at fairs that are subject to strict security regulations that are subject to HSE testing.
Health and Safety Director Spokesperson said, "We are aware and are doing primitive examinations."
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