The crash occurred at 5am on the corner of Tay and Clyde Sts, the intersection of State Highways 1 and 6.
A Fire and Emergency New Zealand spokesperson confirmed Invercargill crews were called to the scene to assist emergency services and extinguish a fire that had started in the engine bay of the car.
The vehicle had overturned, trapping its three occupants inside the vehicle.
Crews arrived on scene within a few minutes. It took about 35 minutes to successfully remove the vehicle's occupants who were then taken to Southland Hospital - two in a critical condition and one in a serious condition.
Late this morning a Southern District Health Board spokesperson confirmed two 18-year-old males had been airlifted to Dunedin Hospital, where they were in intensive care units.
Police confirmed a third occupant, aged 17, remains in Southland Hospital with non-life-threatening injuries.
Fire and Emergency New Zealand shift manager Andrew Norris said the matter was now in the hands of police.
A police spokesperson said the 2005 silver Nissan Bluebird had been travelling at high speed.
Police have appealed to anyone who may have witnessed the car any time before the 5am crash.
The intersection was partially opened to traffic about 10am.
- additional reporting Toni McDonald
