A 17-year-old boy has been stabbed to death at a house party in Leeds.
West Yorkshire Police said officers were called to a disturbance at a property in Salisbury Grove, Armley, where a “large number of people” had been gathered, at around 2.48am on Sunday.
The teenager, from Leeds, was taken to hospital where he was pronounced dead a short time later.
Officers dispersed people from the area and said no arrests have been made.
West Yorkshire Police are treating the death as murder and a crime scene is in place at Salisbury Grove as forensic teams investigate.
Detective Chief Inspector Alan Weekes said police want to speak to anyone who was at the party or anyone who might have footage from the area in the early hours of Sunday.
He said: “The loss of a young life in such sudden and violent circumstances is an absolute tragedy and we are treating this incident very seriously and doing everything we can to identify those responsible.
“We are continuing to support this young man’s family at what is clearly an incredibly difficult time for them, and we are committed to getting them the answers they need as we progress our enquiries.
“Our investigation is still in its very early stages and we are carrying out extensive inquiries to build up a picture of the full circumstances of this incident.
“We are aware there were a large number of people attending a party at the address when the victim was attacked, and we are keen to speak to anyone who was there and who witnessed any part of this incident.
“We would also like to hear from anyone in the area around the time of the incident who has any relevant CCTV, phone or dashcam footage that could assist the investigation.”
He added that officers would maintain an increased presence in the area to reassure the local community.
Anyone with information has been urged to call 101 quoting Operation Pedalbourne, or to get in touch via the West Yorkshire Police website.