A chemical spill is now under control at the Oji Fibre Solutions Tasman Mill in Kawerau.
A Fire and Emergency northern communications spokesman said fire appliances left the scene about 2.30pm and left it in the hands of the mill.
There had been spillage of "green liquor" which was a byproduct of the pulping process.
He said no details on the cause of the spill or any effects were available yet.
Two fire appliances from Kawerau and two from Rotorua as well as a hazardous material unit attended the incident.
Earlier a Fire and Emergency northern communications spokesman said it was "quite a large spill but it is not currently impacting on the environment."
"We are working in conjuction with the emergency response team at the mill."
The mill is one of two pulp and paper mills in Kawerau.