Hamilton firefighters had to intervene between a couple who started arguing after a fire began in their car.
The fire had engulfed the whole vehicle by the time firefighters arrived, northern fire communications shift manager Jaron Phillips said.
The car was parked in the driveway of the Opoia St, Hamilton East home, when the fire began about 10pm, he said.
Mr Phillips said an ambulance was called to check out injuries to one of the people involved.
"While they were there, there was an assault and an ambulance was called for and the brigade intervened and the incident was left with police."
It was initially being treated as suspicious, but Hamilton police Senior Sergeant Andrew O'Reilly confirmed it was an electrical fault.
Mr O'Reilly said the car started running poorly after the couple had installed a stereo in the car.
The electrical fault then caused the fire, he said.
The couple then began arguing and attending firefighters had to step in.
There were no arrests.