Firefighters are battling a blaze at Auckland University's Maidment Theatre.
Vice-Chancellor Stuart McCutcheon told the Herald he did not believe anyone was injured during the fire.
A small group of people were inside at the time.
It was unclear how badly-damaged the building was.
One person suffered a small cut to their hand after smashing the fire alarm, but it's understood they did not need medical treatment.
Fire assistant area commander Roger Callister said the theatre's stage curtains caught fire first and it spread to the roof.
Firefighters were still assessing the damage and were working to identify the cause.
Princes Street was cordoned off by the fire service and police and at least a dozen fire engines were at the scene.
Dozens of students had gathered outside the theatre and were taking photos on their phones.
Fire crews from Ponsonby to Papatoetoe are being called to back up central city fire crews.
- NZ Herald staff