Seven people were taken to hospital on Saturday after a vehicle crossed the centre line and collided with two other vehicles on State Highway 2 near Hastings.
Police were called to the scene of the crash, near the Stock Rd intersection, just before 4pm and initial reports cited up to 10 people were in the vehicles involved in the crash.
Senior Constable Cory Ubels of the Hawke's Bay Serious Crash Unit said the head-on crash saw a vehicle heading northbound cross the road's centre line and collide with two vehicles that were southbound.
A Hawke's Bay District Health Board spokeswoman said as of this morning the conditions of those involved were a female in her 40s in a critical condition, two males in their 20s in a serious condition and a woman in her 20s in a stable condition.
Two children aged between 2 and 4-years-old, a boy and a girl, were also taken to hospital but have since been discharged.
A fire service spokesman said firefighters had to use the jaws of life to free four injured people who were trapped in the wreckage.
The crash was located south of Pakipaki and Mr Ubels said emergency services attended the scene until 5.45pm, with traffic flowing again at 5pm.
Mr Ubels said the cause of the crash was yet to be established and investigations were underway.
"There were some really nice people at the scene that helped assist emergency services," he added.
A restricted speed limit was put in place while oil was cleaned up off the road.