Spilled bitumen is being removed by hand after the boiling mess overflowed from a factory tank into an Auckland stream this morning.
Firefighters discovered the spill at Thermakraft Industries on Turin Place in Otara after responding to an alarm about 9.50am.
The boiling bitumen covered an area about 15m by 25m inside the factory and leaked to an area about 10m by 10m outside, fire service communications shift manager Megan Ruru said.
No one was injured in the spill.
The fire service attempted to stop the spill by covering it with dirt.