Three people are in a critical condition and four seriously injured after two vehicles crashed in Waipu, Northland.

The crash occurred shortly after 1.30pm yesterday.

The route has been the main one for cars travelling to and from Northland due to road works on State Highway One over the Brynderwyn Hills.

Police have confirmed that their initial understanding is seven people are injured.

St John said nine vehicles were sent to the scene, treating and transporting seven patients.

Three patients were taken to Starship Children's Hospital in Auckland, one in a critical condition and two in a serious condition, and four were taken to Whangārei Hospital. One person in a critical condition was taken by helicopter.

Three helicopters were dispatched, five ambulances, two rapid response units and two operations managers.

St John confirmed three patients were critically injured while four were seriously injured.

Whangarei's mayor Vince Cocurullo said the road the crash happened on was not usually dangerous.

Up until now, the detour route has been going smoothly, and traffic has travelled well below the speed limit, he said.

Waka Kotahi NZ Transport Agency said the crash had occurred near Johnson Point Road and closed Cove Road between McLean and South roads.

One dead in separate crash

One person has died following another crash in Northland yesterday.

The two-vehicle crash happened at the intersection of State Highway 1 and Apotu Road in Kauri.

It was reported to police at 3.13pm.

Police said one person was critically injured and died at the scene.

"Police extend our condolences to their family and friends at this time."

"The Serious Crash Unit will conduct a scene examination, and motorists are asked to avoid the area."

This story was first published by RNZ