A park stunt in which two girls were thrown from a roundabout powered by a moped is being investigated by police.
The roundabout was powered using the back wheel of a motorcycle
Officers were alerted to the incident in Crawley, West Sussex, after seeing video footage of the prank on a US-based website.
The video shows a spinning motorcycle wheel being placed on the outer edge of the roundabout by two teenage boys. Two girls are crouched in its centre.
Insp Mark Piper said the stunt was similar to a "high-speed road crash".
The roundabout eventually reaches a speed of about 20mph (32km/h) and the girls, believed to be 12 or 13 years old, are flung off violently.
Mr Piper added: "This is an extremely dangerous practice and for the safety and welfare of all concerned we are urgently trying to contact and speak to the participants."
A spokesman for Crawley Borough Council described the stunt as "phenomenally dangerous" and said it could have ended in a fatality.
"It is a bit like Jackass but this is a lot more dangerous because it involves children rather than people old enough to know better," he said.
"We have checked local hospitals and we have been assured that no emergency admissions have been made relating to this."