A witness who arrived at the scene soon after the crash said a ute and a white sports car had clearly collided, but a lorry was also pulled over to the side of the road.
"It happened on a bend going over a bit of a hill and they met at the top of it - so they were possibly overtaking in a stupid place. If so, that's a terrible place to overtake."
He had overheard a police officer saying the teenage driver of the white car did not have a licence, he said.
"I think the guy in the ute survived but he was in pretty bad condition - they choppered him to hospital."
A St John spokesman said two of those hurt were seriously injured and another had moderate injuries.
State Highway 1 has been closed, and a detour is place but is not suitable for heavy vehicles.
The St John spokesman said three ambulances and a helicopter had been sent to the scene, and would take the patients to Christchurch Hospital.
Three fire trucks were also at the scene of the crash on Glasnevin Rd.
State Highway 1 is closed between Watties Rd and Innes Rd and diversions are in place.
Police said severe delays were expected and asked motorists to avoid the area as the closure would remain in place for several hours.
The Serious Crash Unit is investigating.
The Hurunui District Council said the detour was not suitable for heavy vehicles and people should avoid travelling if possible.
The crash brings New Zealand's road toll for March to 21, after a person was killed in a crash in Reporoa near Taupō last night.
As of Friday, 86 had been killed on our roads this year, compared to 74 this time last year.
