A fire brigade van carrying three volunteers flipped, after it collided with a turning car on State Highway 6 at the Pisa Moorings Rd intersection yesterday.
Police are investigating the crash.
There was a "strong possibility" charges would be laid in relation to the accident, Cromwell detective Gary Hyndman said.
Volunteer firefighter Norman Jermyn sustained multiple leg fractures and was airlifted to Dunedin Hospital by helicopter after paramedics, Cromwell doctors, and his own fire brigade colleagues rushed to his aid.
Mr Jermyn, an operational support fire officer and Otago Daily Times paper delivery worker, was a passenger in the front seat of the van.
He was travelling with two other volunteers when their vehicle collided with a car at the Pisa Moorings intersection.
A 73-year-old Invercargill man, the driver of the hatchback, was taken to Dunstan Hospital with head injuries and lacerations after he was rendered unconscious by the impact.
The man was travelling north along SH6 with his elderly wife and 6-year-old grandson in the back seat when the crash occurred.
The passengers in the hatchback were not injured.
The 34-year-old van driver had a head wound stitched.
The remaining passenger was not injured.
Det Hyndman said the brigade van was travelling north on SH6 to the fire callout with its emergency lights flashing.
The van was not equipped with sirens.
The hatchback had been stationary in the middle of SH6 and had turned right into Pisa Moorings Rd when the collision occurred.
The hatchback had its right indicator on at the time of the crash, Det Hyndman said.
He declined to discuss which driver was likely to be charged.
The 111 callout at Parkburn Quarry was found to be a permitted burn-off.
Cromwell brigade members turned back to give assistance to the injured crash victims upon notification of the accident.
St John ambulance staff, paramedics, and Cromwell doctors arrived shortly afterwards.
Cromwell fire chief Steve Shaw said brigade members cut the roof from the rolled van to free their mate.
Firefighters dealt with any accident involving a colleague "just the same as any other".
"It's never nice when there is [an accident] which involves one of your own, but you just get in there and do it."
Firefighters were trained to respond to rescues and got on with the job at hand, he said.
The accident is the second in less than a week involving a Central Otago volunteer fire brigade member.
Central Otago rural fire authority officer Kenneth McGarry was trapped for two hours on Saturday in the driver's seat of an 8000-litre tanker.
A driveway collapsed beneath it and it rolled down an embankment during a fire call-out in Alexandra.
