Two fire crews, as well as police and ambulance were at the scene.
One other person is in a moderate condition, a St John spokeswoman said.
Waikato police Senior Sergeant Pete van de Wetering said the road was closed diversions were in place at both ends of Steen Rd.
In a second serious crash on SH2 today, one person is critically injured after a two car crash on the highway, south of Katikati.
Two ambulances are at the scene, and one other person has minor injuries, a St John spokeswoman said.
Police said at least three people were involved in the crash.
Emergency Services were called to the scene at 8.15am.
A fire service spokeswoman said crews were assisting with traffic control.
SH2 is closed south of Katikati and detours are in place via Marshall Rd and Tetley Rd.
The police Serious Crash Unit is investigating both incidents.