A murder investigation has begun into the death of a man found fatally injured in Luton on Saturday.
The man, who has not been named, was found severe chest injuries in a flat in High Town Road.
A Bedfordshire Police spokesman said he died shortly after arriving at Luton and Dunstable Hospital.
The house has been sealed off and forensic teams are carrying out a fingertip search of the property.
Officers found the dying man when they were called to the premises at around 1510 GMT.
Four youths
The spokesman said they particularly wanted to trace four black youths seen running away from the property around the time the man was attacked.
The four ran from High Town Road, down Cobden Street and across the grounds of St Matthew's School where they had an argument.
Deputy senior investigating officer Lennox Lamb said it was possible the four had been seen running towards the town centre.
"This is horrendous attack which has resulted the senseless of loss of a man's life," he said.
Detectives have urged anyone who was at the house earlier in the day, or at the time of the incident, or who knows the identity of the four to call them in confidence.
A post-mortem examination is to be carried out to establish the exact cause of death.