A 25-year-old man has been arrested in connection with the death of a Paraparaumu teenager, police say.

The Kapiti man will appear in Porirua District Court on Monday charged with assault, the officer in charge of the investigation, Detective Inspector Mike Johnson, says.

Izak Millanta, 17, died at 2.30am on Sunday in Wellington Hospital after being found unconscious in a Coastlands shopping mall carpark around 3am on Saturday.

Det Insp Johnson says an autopsy is under way to establish the cause of death.

Police have spent much of Sunday speaking to witnesses about an altercation involving Izak outside the Retro Bar near where he was found.

"If there is anyone who is holding on to information in relation to this incident and has not spoken to police yet, I urge you to come forward and speak with us," Det Insp Johnson said.