A police forensics team has been searching London Road in St Albans following the teenager's death
Nine people, including a 16-year-old girl, have been arrested over the death of a teenager after an "altercation".
The victim, who was 19, died in Watford General Hospital after being hurt in London Road, St Albans, Hertfordshire, at about 03:20 BST.
All nine people remain in custody and police have appealed for witnesses to come forward.
Det Insp Justine Jenkins said the incident would have "attracted attention of anyone" nearby.
The force said it did not expect to name the victim or release any details of his injuries at this stage.
Girls, aged 16 and 17, have held by police alongside men and women in their 20s.
London Road has been shut while investigations continue.
The police helicopter has been flying over the area.
A tent has been put over a car on London Road
London Road has been closed while police carry out inquiries
Police said officers responded to reports of an "altercation" at about 03:20 BST
Police have appealed for witnesses to contact them and officers are still at the scene
