Fire and Emergency shift manager Murray Dunbar said six appliances and two tankers from North and South Taranaki had joined those from New Plymouth to fight the fire.
About 24 crew members were onsite and Dunbar estimated at least 40 would be fighting the blaze as extra resources arrived.
Smoke from the large fire at Taranaki By-Products plant in Okaiawa could be seen across Taranaki. Photo / Brad Roberts
Dunbar said the fire posed no risk to other properties as the plant was located in a rural area. There was a section of the plant which was not in flame. Dunbar said it would likely not be impacted.
A man based in Hāwera said he saw thick, black smoke rising from Okaiawa and rushed to the scene.