Police in Waikato say a farmer who extinguished  a fire after a fatal car crash may have saved a woman's life.

A 47-year-old tourist  died in the crash in Benneydale, south of Te Kuiti on Tuesday, while her 45-year-old sister  was trapped in the car until the Fire Service arrived.

Police say a farmer, who arrived on the scene soon after the crash, potentially saved the woman's life by putting out a small fire in the car's engine.

The woman is in hospital with serious injuries.