A 16-year-old boy has been arrested on suspicion of murder following the death of another teenager in Milton Keynes.
Thames Valley Police said officers were called to reports of an altercation in Tyburn Avenue, in the Springfield area of the town, at around 6.40pm on Saturday.
A 17-year-old boy was taken to hospital from a street nearby after sustaining injuries to the chest, but later died, the force said.
His next of kin have been informed and are being supported by specialist officers.
The teenage suspect, from Milton Keynes, was arrested and remains in police custody.
A large police presence was in the area on Sunday and will remain there for some time while officers conduct door-to-door inquiries, the force said.
Chief Inspector Kelly Gardner said: "First and foremost, our thoughts are with the family and friends of the boy who has lost his life.
"There will be an increased police presence in the area while inquiries are carried out as part of a thorough investigation. This will include our neighbourhood police officers, who will be in the area all week.
"If you have any concerns feel free to approach and talk to these officers."
Senior Investigating Officer, Detective Chief Inspector Stuart Blaik added: "We are currently working to establish the circumstances of this incident in which a boy has tragically died.
"I would encourage anyone who has information about what may have happened to please come forward as well as those who may have been in this area between 6.25pm and 6.50pm."
Police are appealing to anyone with potential CCTV or dash-cam footage of the area to check for anything that may assist the investigation.
Information can be provided by calling 101 or by making a report online, quoting reference number 43200364814.
Alternatively, information can also be given anonymously through Crimestoppers on 0800 555 111.