They later said the dead included an adult and a child.
Two adults and another child are among the injured.
“Our thoughts are with their family and friends at this sad time,” a statement from police read.
“Police would like to thank the members of the public who responded and assisted with this tragic incident, taking control of the scene until emergency services arrived.
“The full circumstances of the crash are now under investigation and at this stage.”
Emergency services were called to the two-vehicle crash at around 12.42pm.
The Serious Crash Unit are in attendance and a scene examination is underway.
“Hato Hone St John [is] responding to a traffic-related incident on SH1 near Mangaweka. Multiple ambulances and helicopters are currently responding to [the] scene,” St John said initially.
Multiple people seriously injured
In the latest update, Hato Hone St John said paramedics treated three people. Of those, two victims - one critically injured and the other in a serious condition - were airlifted to Wellington Regional Hospital.
A third person suffered moderate injuries and was taken via ambulance to Palmerston North Hospital.
New Zealand Transport Agency Waka Kotahi confirmed the crash was a “fatality”.
The crash blocked SH1 north of Mangaweka and the road was closed for several hours to southbound and northbound traffic.
Diversions were put in place via SH4, a two-hour diversion.
SH1 was reopened shortly before 5.30pm.
New Zealand Transport Agency Waka Kotahi called the incident a “serious crash” near the intersection of Ruahine Rd.
“NZTA thanks all drivers for being patient on the detour route, which will be busy. If people can delay travel today that will help ease congestion on the detour route.”
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