Eli Francis Holtz died after being assaulted in Auckland on Saturday night.

A teenager assaulted while sitting in a car at traffic lights has died, sparking a homicide investigation.

Eighteen-year-old Eli Francis Holtz was assaulted at the intersection of Wellesley St West and Queen St in central Auckland at 3.15am on Saturday, police said.

He was taken to Auckland City Hospital and put on life support, but died at 8.45pm on Sunday.

NZ POLICE Police say the passengers of this white Prius may have witnessed the assault.

Police said a 30-year-old man had been arrested and charged with wounding with intent to cause grievous bodily harm.

He would reappear in the Auckland District Court on Tuesday, when the charges were expected to be upgraded.

Tributes were flowing for the teenager on Facebook on Monday.

NZ POLICE The three men who police would like to speak to. It is believed they caught a bus to Takapuna shortly after the incident.

"Gone way too soon but never forgotten," one woman said.

Another man wrote: "Rest easy up there in heaven brother Eli. Love you my bro."

Police said they wanted to speak to the occupants of a white Toyota Prius that was behind the vehicle Holtz was in at the time of the assault.

A post mortem examination was being carried out on Monday, with police investigating CCTV footage.

Police also said they would like to speak to three men who were at the intersection at the time of the incident and may have witnessed the assault.

It is believed those men caught a bus to Takapuna a short time later.

Anyone else who may have witnessed the assault is being urged to contact Auckland Central Police on (09) 302 6400 or Crimestoppers anonymously on 0800 555 111.