Emergency services responded to the single car crash near the intersection of Taieri Rd, Kaikorai Valley Rd and Stuart St about 2.40am today.
Fire and Emergency NZ shift manager Simon Lyford said two appliances initially responded, with a third called to help free the trapped driver.
A St John spokeswoman said the four occupants were taken to hospital - one in a serious condition and the rest in moderate condition.
Police could not confirm if alcohol was a factor and said inquiries were ongoing.