Papakura constable Jenny Sinclair says she just "acted from instinct" when she and a neighbour pulled an injured man from a burning car on Friday night.

Sinclair, 32, and the neighbour, who rang police after he heard the car crash on the Papakura-Clevedon Road, risked their own lives by leaping in when the driver's side of the car was already in flames.

Just seconds after they pulled the injured driver out through the passenger door, the car exploded.

"As we dragged him out of the vehicle it basically took hold of the vehicle and the whole thing went up," she told the Herald on Sunday yesterday.

"If it was a few seconds later, we would have had to consider our own safety.

"I was just acting from instinct. I was just doing what any member of the police would do."

The neighbour heard the crash and called police at 3.47pm on Friday.

"He still had a bit of distance between where he lived and the crash, so he was waving me down when I pulled up," Sinclair said.

The car had spun off the road across two paddocks and the pair could see the fire as they ran through long grass to reach it.

"It was fairly well engaged on the driver's side, with the whole front to back on that side, and it was really long high grass so we couldn't really get at the driver's door because the flames were coming out from around the back of the vehicle. So the only option was to try and pull him out through the passenger side," Sinclair said.

The driver was unconscious with "a really significant head injury on the side of his head".

"So I managed to get his seatbelt off and I managed to rouse him enough to encourage him to start trying to climb out," she said.

"He leaned over enough so that we could grab his arms and pull him out on to the grass, and then it started to burn very intensely and we had to keep pulling him back away from the vehicle."

"I was leaning in to pull [the driver] out, I managed to get him part-way across the passenger seat, and the other guy came around to help," she said. "We grabbed an arm each."

Amazingly, neither Sinclair nor the neighbour was hurt. But the driver, a 27-year-old man who lives in the area, was taken to Auckland Hospital where he is now in a serious but stable condition.

"He had lost quite a bit of blood from the head wound," Sinclair said.

When she and the neighbour shook hands afterwards, their hands were covered in blood.

"I have spoken to the member of the public today and he is still really shaken up and overwhelmed by it all, but we both agreed that we couldn't have lived with ourselves if we hadn't tried," said Sinclair, who has been in the police force for eight and a half years.

"I don't want to have any media attention on it because it takes away from the fact that I was just doing my job, and I would expect anyone in uniform to do exactly the same thing.

"It's actually what we come to work for."