The highway, at the intersection with Hannah Rd, was closed for several hours after the crash but police and the NZ Transport Agency confirmed about 3.50pm that it had reopened.
The Serious Crash Unit was investigating.
A Hato Hone St John spokesman earlier said four people were taken to hospital by ambulance.
Three were in critical condition and one in serious condition.
The road was blocked at the intersections of SH30, Lee Rd and Robinson Ave, causing traffic to build up as heavy vehicles such as logging trucks needed to be diverted back towards Ngongotahā.