A 17-year-old boy suffered life-threatening injuries after being stabbed in the grounds of a £1.5m house in rural Sussex.
The teenager was stabbed in the chest in the early hours of Sunday morning after a large gathering of young people near Balmohano Farmhouse in Warnham.
Later, a 16-year-old boy was arrested on suspicion of attempted murder. He remains in custody.
Sussex Police described the victim’s condition as “critical”.
Crime scene photographs show police tape surrounding a collection of white tents, draped with flags, in the middle of a field, with a portable toilet nearby.
Police have said “many young people attended” and that it was an “isolated incident” with no further risk to the public.
Detectives are speaking with parents and local schools.
plea for information
Ch Superpt Jo Banks said: “We urge witnesses and anyone with information to come forward.
“We understand that there were many young people in attendance at this address at that time who will learn important information to help the investigation.
“In particular, we would also ask parents and caregivers of attendees to speak with their children and contact us with information.
“This is a complex and fast-moving investigation.
“Officers will be working in partnership with local schools and there will also be an increased police presence in the area to provide reassurance.
“We believe this was an isolated incident that does not pose a broader threat to the community.”