A 70-year-old man is dead after crashing his car in the South Waikato this morning.

A witness told police the man drove straight off the road in Fitzgerald Glade, 40km northwest of Rotorua, shortly before 8am, Senior Sergeant Gary Barber of police northern communications told NZPA.

Mr Barber said the single-vehicle crash may have been caused by a medical problem, but police were waiting on confirmation from crews at the scene.