Firefighters are working to cool a furnace fire at the Tomago Aluminium Smelter.
Crews from Mayfield West, Tarro and Raymond Terrace and an RFS crew were called to the smelter just after 1.00am on Wednesday and immediately liaised with an emergency response team on site.
A small fire at the top of a furnace caused the temperature to rise to 700 degrees Celsius - electricity and gas supplies to the furnace have been isolated, however the fire has reignited several times.
A spokesman for Fire and Rescue NSW says crews are unable to use water on the fire because the mix of water and molten aluminium would create explosive hydrogen gas.
The furnace has now cooled to 280 degrees.
There's no immediate threat to surrounding properties, however it's likely to take several hours before the incident is fully contained.
