Meanwhile, three people were reported to be trapped in vehicles following a crash on the Kapiti Coast.
Emergency services are attending the two-car crash in Raumati South - on State Highway 1 between the Whareora Rd on-ramp and the Kapiti Expressway about 6.45pm.
St John said one person was in a critical condition, two were in a serious condition and four had minor injuries.
A helicopter was called to the scene along with six ambulances.
The northbound lane is blocked, and the Police Serious Crash Unit is attending.
Motorists heading north on SH 1 out of Wellington are advised of delays and asked to delay their journey if possible.
Motorists are also fearing for the worst in Auckland, with two crashes within 20 minutes of each other.
A single vehicle reportedly rolled on Henderson Valley Rd, between Pine Ave and Candia Ave, just before 8pm.
The occupants were out of the vehicle when emergency services arrived, and received moderate injuries.
Inquiries are ongoing.
Emergency services were also called to Longford Park Dr, in Takanini, at 8.20pm to a report of a single car hitting a pole.
The sole occupant was reportedly trapped for a time, and in a serious condition.
They were taken by ambulance to hospital and inquiries are ongoing.