Plumes of black smoke can be seen in Papakura as a fire takes hold of a scrap metal yard.
Workers from nearby businesses are evacuating the scene.
People have been posting on social media from as far away as Pukekohe saying they can see the smoke from the blaze.
A witness said there was a “definite plastic/chemical smell.”
Fire services were called to the scene on Hunua Rd just after 8am.
A northern fire communications spokeswoman said they got the first report of the blaze at 8.03am.
A total of 10 fire trucks and two helicopters are helping at the scene as well.
Fire and Emergency ENZ confirmed they are at a scrap metal yard and the size of the blaze is currently measuring about 25m by 15m.
There are no reports of injuries, the spokeswoman said, and there is no danger to any neighbouring properties at this stage.
St John paramedics are there as a precaution, a spokesman said.
Police have been notified of the incident and are helping FENZ with traffic management.
Motorists in the area are encouraged to stay away. Police have closed off a section of Hunua Rd between Parker St and Boundary Rd. Diversions are in place.