The area around Tory Street, between Courtenay Place and Wakefield Street, has been cordoned off.
There were no cars or people in the parking building, as it was being earthquake-strengthened after earlier damage as a result of an earthquake in 2013.
Speaking to Checkpoint with John Campbell, Mayor Justin Lester said the building was badly damaged in the 2013 quake, and engineers said today it should be closed.
He said it was likely beyond repair and would need to be taken apart and come down.
Mr Lester said scores of people had been told to evacuate.