The blaze broke out at about 2pm and was contained about 90 minutes later.
It's now 12 hectares in size.
Fire crews were alerted just before 1:30pm on Friday to the vehicle fire.
A welfare centre for evacuated residents has been set up.
The smoke could be seen from several kilometres away.
Emergency services responded just before 11pm on Friday, police say.
All four fires have been extinguished.
Fire and Emergency and WorkSafe are both warning of the risks of the heater.
Three helicopters were called in at first light to help control the blaze.
