Two people have died following a serious crash on State Highway 3 at Kaitoke, just south of Whanganui.
Two people were also critically injured in the collision.
According to Police, emergency services were first alerted to a report of a crash involving two vehicles around 5.30pm on Thursday evening.
By the time first responders arrived at the scene, two people had died.
A third person involved in the crash was airlifted from the scene to Palmerston North Hospital in a critical condition.
That patient has since been transferred to Christchurch Hospital via air.
A fourth person, an 18-year-old male, was transported via ambulance to Whanganui Hospital in a serious condition.
The DHB confirmed on Friday morning that the 18-year-old's condition had deteriorated, and he was in a critical condition.
As of Friday afternoon, the 18-year-old was in a stable condition, awaiting surgery.
Waka Kotahi NZ Transport Agency says the crash happened near the intersection with Pauri Rd.
State Highway 3 was closed from the Pūtiki roundabout shortly after the crash, with a detour in place via Fordell.
The road has since reopened after a scene examination by the Serious Crash Unit.
An investigation will follow into the circumstances of the crash.