Emergency services responded to a two-vehicle crash at the corner of Thames and Wear Sts at 7.42am. A St John spokeswoman that said three people were injured and one was flown to Dunedin Hospital in a serious condition.
Two other patients, one in a moderate condition and the other having minor injuries, were taken to Oamaru Hospital.
A police spokeswoman said it was believed one of the drivers had a medical event.