Hilary Barry tweeted about the evacuation from a nearby pub.
"Fire alarm at TVNZ. And yes, I admit this is the view from inside at The Empire," she wrote.
Shortly before 3.30pm Nicholson said a second alarm had been triggered by crews at the downtown site, requesting more assistance.
Three further fire trucks and an aerial appliance were en route to central Auckland, with a total of eight appliances responding.
A small fire in the building appeared to have been extinguished by the sprinkler system, Nicholson said.
The requested trucks were stood down and crews left the site shortly after 4pm.
Te Karere earlier told viewers to stand by for details on whether the daily MÄori news station would go to air in 40 minutes.
One TVNZ viewer reported that their television services appeared to have stopped as the building was evacuated.
Police did not attend the incident, a spokesman said.
TVNZ tweeted in response that it was experiencing interruptions to its regular service and was resolving the issues as quickly as possible.
A TVNZ spokesperson confirmed staff had been evacuated from the building shortly before 3pm after a fire alarm was triggered.
"TVNZ 1 and 2 were off air momentarily, but service has now been restored."
At that stage there was no impact to TVNZ's scheduled afternoon and evening news programming, she said.
