A teenager who died after being stabbed has been named as Louis-Ryan Menezes.
Northamptonshire Police launched a murder investigation on Friday after the 17-year-old died in Drayton Walk, Kingsthorpe, Northampton.
Three people arrested on Saturday have been released without charge. The force did not say what they had been arrested on suspicion of.
Det Ch Insp Karl Whiffen said he was "keeping an open mind" as to the motive for the attack.
Mr Menezes was pronounced dead at Northampton Hospital.
A post-mortem examination found he died from a stab wound to the chest.
Det Ch Insp Whiffen said they had a "large team of specialist officers working round the clock to identify and bring to justice whoever is responsible for killing Louis".
"We are keeping an open mind as to the motive and we need the public's help to enable us to track down whoever is responsible for ending his short life," he added.
Police have appealed for anyone who was in the Eastern Avenue North or Newnham Road areas of Drayton Walk between 18:00 and 19:00 on Friday to contact them.