Smouldering batteries in a Rocket Lab warehouse near Auckland Airport have exposed six people to a chemical.
Three fire engines and 16 firefighters attended the scene on Airpark Dr on Sunday night.
Auckland fire region assistant area commander Mike Shaw said they were called to the scene regarding smoke emanating from a bank of batteries in the warehouse.
"There is no fire in the batteries, but there was a rise in temperature that caused smoke to emanate from the batteries."
Mr Shaw said firefighters would remain at the scene until the batteries returned to a normal temperature.
St John shift supervisor Patsy Carlyle said six patients were exposed to a chemical.
"We have assessed all of them and none of them require transport at this stage."
Rocket Lab confirmed the incident in a statement on Monday morning.
"No one was injured and there was no fire. The fire service attended as a precaution while the batteries returned to a normal temperature."