A 44-year-old Papamoa woman and an 11-year old Papamoa boy from the same car were also taken to hospital with minor and moderate injuries.
All three remained in stable conditions in Tauranga Hospital last night.
The two occupants of the van, believed to be a 61-year-old woman and a 65-year-old man, escaped the crash with minor injuries.
Head of Western Bay road policing Senior Sergeant Ian Campion said the two cars were travelling north, towards Katikati, and the van was travelling south, towards Tauranga.
A vehicle had crossed the centre line and crashed into two oncoming vehicles, he said.
Serious crash analysts were called to the scene yesterday and investigations were continuing, he said.
Three overseas workers were in a neighbouring property when the crash happened.
One, a German man, said he heard a huge crash before the three of them ran to the road.
It was a terrible sight, he said.
After helping where they could, the three men stood near a collection of white crosses for victims of a previous crash and watched as emergency services worked.
The farm owner said he had campaigned for nine years to get the winding stretch of road down to 85km/h but it still was not slow enough.
Serious and fatal crashes were common there, he said.
Traffic was diverted around the crash site for more than three hours.
Heavy vehicles were unable to use the detour and a line of trucks built up at the road closure until the section of SH2 was opened to all traffic about 3.30pm.
Mr Campion previously told the Bay of Plenty Times SH2 between Bethlehem and Athenree was the worst stretch of highway in the Western Bay.
Three people had already died there this year.
In the five years between 2009 and 2013 there were four fatal, 26 serious and 72 minor crashes on the stretch between Tauranga and Waihi.
Although the road was straight, most of the crashes were caused by drivers crossing the centre line or making a poor gap selection when pulling out of side roads, Mr Campion said. High traffic volumes and commuter traffic in the early morning and evenings were also contributing factors, he said.
The stretch of highway was receiving the "lion's share" of the police staff deployment during this year's winter road safety campaign.