An 11-year-old boy has suffered serious head injuries after being involved in an incident with a playground swing.
Kieran Snee suffered serious injuries after hitting his head on the metal support of a swing while playing with his 10-year-old cousin at Denes Park in Darlington on Friday.
Police would not comment on reports that Kieran was injured during a so-called playground game of "bumping", in which the objective is to bump the basket against the metal support frame.
A 15-year-old girl has been arrested on suspicion of causing grievous bodily harm and released on police bail, a spokesman for Durham Police said.
Police said the youngster underwent surgery at James Cook University Hospital, where he is in a critical but stable condition on a life support machine.
His parents remain at his bedside in hospital.
The boy's parents said their "world had been turned upside down" since the injury to their "lovely, playful boy who would not hurt a fly".
They added that Kieran's 10-year-old cousin had been "extremely brave" throughout the ordeal.
They said they were overwhelmed by the support they had received from the police, hospitals and members of the public.
Police have appealed for any witnesses to the incident to contact them.