A teenager found on a Nottingham street died from a single stab wound to the chest, police said.
The teenager was found injured in the street
Officers have begun a murder inquiry following the death of 17-year-old Jason Spencer of Montfort Crescent.
A post-mortem examination showed the teenager, who was found on Tithby Drive on Tuesday, died from a stab wound.
A 19-year-old man was arrested at the scene and is being questioned by police in connection with the incident. The area has been cordoned off.
The victim was taken to the Queen's Medical Centre but was pronounced dead on arrival.
Detectives are trying to trace a man seen leaving the scene on a mountain bike shortly before police arrived.
They said he may have information regarding the death.