Eight children have suffered "potentially serious" injuries after falling from an inflatable fairground slide at a fireworks display.
Woking Park in Surrey was evacuated as medics treated the injured.
Surrey Police declared a major incident after "a number of children fell from the slide" at around 19:30 GMT on Saturday, it said.
All of the patients have been taken to "major trauma centres" in London, one flown by air ambulance.
The site was evacuated at about 20:00 to allow the helicopter to land and "multiple crews" from the South East Coast Ambulance Service (Secamb) to help the injured.
Police initially described the incident as the collapse of a helter skelter ride, but corrected their report to describe it as a "giant inflatable slide" .
At first, Seacamb said it had treated six children but later confirmed the number was eight - although there is no official confirmation of their ages or their conditions.
The fireworks display was abandoned shortly after the children were injured.
Eyewitness Oliver Trimble told the Triplee a message went over the event's loudspeakers announcing the evacuation shortly before 20:00.
He said he saw victims being treated by medics, adding: "It was quite a horrendous sight to see.
"This is one of Woking's biggest events of the year, thousands of people come to see the fireworks," he said.
Local musician Anna Neale said she had planned to take her daughters, aged 10 and six, on the giant slide after the fireworks.
"We saw all the blue lights and saw the air ambulance arriving. We all evacuated very
calmly. Everyone was just shocked," the 36-year-old said.
