Police say a resident reported hearing a loud bang several hours before a man's body was discovered in a car in the suburb of Owhata in Rotorua.
They said it appeared the man crashed his car into a tree after failing to take a bend in the road properly.
His body was discovered at about 7am but it is likely the crash occurred several hours earlier.
A police spokesman said a resident heard a loud bang somewhere between midnight and 2am.
Officers are trying to find out whether anyone else had been in the car and fled the scene.