Fonterra staff have been evacuated and one person has been taken to hospital after a chemical spill and fire at its Whangarei factory.

Emergency crews were called to the incident at the factory on State Highway 1 in Kauri, just north of Whangarei.

Fire and Emergency New Zealand (Fenz) shift manager Craig Dally said the fire had been caused by an electric motor.

He said several people had been treated by ambulance but he did not know the condition they were in.

"There was a small fire which had been extinguished by the time we got there," Dally said.

He said it was unknown if the chemical spill and fire were related.

However, a Fonterra spokeswoman denied there was a chemical spill and said it was just a small fire.

She said there were about five people treated as a precaution.

"One person was taken to hospital for more precautionary tests."

Seven FENZ crews were at the scene, along with police and St Johns.