A boy aged 16 has been stabbed to death in Birmingham.
The youngster collapsed in the street after a dispute involving two teenagers, said West Midlands Police. He is believed to have earlier got off a number 2 bus, but it was not clear if he was attacked in the street or on the bus.
Officers were called to Hayfield Road at the junction of Yardley Wood Road in the Moseley area of the city just after 8.30am.
A West Midlands Police spokesman said: "The lad was taken to hospital by land ambulance in a critical condition but died from his injuries despite the best efforts of medics.
"The motive for the attack remains unclear although initial inquiries suggest that this was a dispute between two teens and not a random attack.
"Detectives are utilising the skills of officers and staff from a range of departments from across the force as part of the investigation and officers are now actively looking for the teen’s attacker."
Officers want to hear from anyone who was travelling on the bus.
Detective Chief Inspector Simon Wallis, who is leading the investigation, said: "A murder investigation has today been launched following a stabbing in which a young man has needlessly lost his life.
"Our thoughts are with the family and friends of the deceased and specially trained family liaison officers are supporting them during this very difficult time.
"We’re working hard to understand the precise circumstances surrounding the attack. At this time it is unclear if the attack happened on the bus or in the street. Because of this I need anyone who was on the number 2 bus this morning around Yardley Wood Road to contact me immediately.
"We are committed to finding the person or people responsible and bringing them before the courts."
The victim's next of kin have been informed and a post mortem is planned.