A police spokeswoman said officers were called at 10.01am today to a collision between two cars at the intersection of Longbush South Rd and Rimu Rd, just east of Invercargill.
At 11.25am police said one person remained trapped in one of the cars and was in a critical condition, but all passengers have now been taken to hospital
Another patient had a head injury.
St John spokesman Gerard Campbell said ambulance officers had treated three patients, one of whom was critically injured, while the other two had serious and moderate injuries.
All had now been transported to Southland Hospital by ambulance.
Three ambulances and a St John manager were called to the crash. A rescue helicopter was called from Dunedin but it was unclear if it was used.
The police spokeswoman said the cars were reported to be upside down and at least one of the vehicles was reported to be on fire.
A man living nearby said he had seen ''flames coming out of the front of one of the cars'' and emergency services were working to free a person trapped underneath one of the vehicles.
That car was upside down at a ditch and fire crews were drawing water from the ditch, but appeared to have extinguished the blaze, he said.
A Fire and Emergency New Zealand spokesman said crews from Invercargill were sent to assist with freeing the people trapped in the vehicles.
