A car was ripped in two on the outskirts of Hamilton this morning, leaving two people in critical condition.
A Waikato District Health Board spokeswoman said one of the men was in a critical condition in Waikato Hospital's intensive care unit, while the other man was in theatre undergoing surgery.
He will then be transferred to the high dependency unit.
A witness who lived close to the crash scene said he and his wife were woken by a loud "whack" and went outside with a torch to find two men trapped in the front half of the car.
"I just heard a whack and as soon as I heard it I knew it was a car crash. It was pretty freaky."
He heard one of the occupants start screaming for help and yelling out the name of his mate, who was unconscious in the passenger seat.
"He just went 'help', and kept yelling out his mate's name, and when I shined the torch on his mate, he just looked like he was dead. But then I saw his chest moving, so I don't know. I was just amazed that they were alive."
The driver had serious leg injuries, he said. "One guy was unconscious and the other guy, screaming, looked like his leg was munted."
The car had been travelling towards Hamilton when the driver has appeared to have lost control and hit a tree on a slight angle, slicing the car in two. The engine came off and landed in a mangled heap on the road, and the rest of the car landed about 30m away, through a fence and in an empty paddock.
"I don't think it hit the tree front on I think it must just have clipped it," the man said.
The man and another neighbour comforted the pair. Firefighters had cut a section of the car to free the men.
"It's amazing man, it was freaky. He was screaming, swearing. My wife rung the ambulance and the neighbours turned up 10 minutes after I got there, she was doing first aid. He was yelling for water, I gave him some, which she said 'nah, don't give him anything'. But he was screaming."
The man said the men looked like they were aged in their 30s and the car they had been driving appeared to have been modified, with two large exhausts and a bigger-than-normal engine.
He said the straight stretch of road was popular for boy racers and speedsters.
It was the second crash he had experienced, in nearly the same spot, since living on the road in the past three years.
Waikato road policing manager Inspector Freda Grace said the car involved was a high-performance Nissan vehicle.
As for a cause of the crash, Mrs Grace said based on the severity of the crash, speed is likely to be a factor.
Both occupants remain in a critical condition in Waikato Hospital.