Police also said it appeared two vehicles were involved - one containing three people and the other six.
Nine ambulances attended the incident and treated patients. The injured people were then transported to Dunedin Hospital.
Two people were in a critical condition following the crash, St John said. Four others were in a serious condition and four had moderate injuries.
At 10.30pm police were still at the scene. One lane is now open and traffic is flowing, police said in a statement.
The Serious Crash Unit is attending and there may be road closures later tonight while the scene is examined, police said.
Northbound traffic was earlier being diverted at the intersection of Fortification Rd and SH1. Southbound traffic was also being diverted, at the intersection of Happy Valley Rd and SH1.