Fire and ambulance crews have responded to an incident in central Auckland where firefighters were decontaminated as a precaution.

Fire and Emergency New Zealand said crews were alerted to an automated fire alarm at a 15-storey building on Anzac Ave at about 5am.

Shift manager Paul Radden said a second alarm was transmitted to bring in additional resources after smoke was found on the fourth floor.

Ten crews were sent to the property and eight were still on site, Radden said.

A hazardous materials unit was sent from Hamilton to assist.

Emergency services attending the incident on Anzac Ave in central Auckland. Photo / Jason Dorday

Herald photographs showed firefighters in hazmat gear being sprayed in a portable shower.

Radden said decontamination was precautionary because unknown contaminants may be on the smoke-affected level.

Hato Hone St John said it was notified of the incident at Anzac Ave at 5.15am today. One ambulance, one rapid response unit and one operations manager attended.

Three patients, all in minor condition, were assessed and treated at the scene (no transport required). The crews have since been stood down.