It was the second such incident at the $34 million multi-level shopping centre, which was developed by the Dunedin City Council and opened in 2009.
A witness told the Otago Daily Times she was having coffee at McDonald's across from the mall about 5.30pm when ''I heard this tremendous noise''.
''Everyone just ran and glass showered down on to the road.''
She said it was lucky no-one was on the road when the glass shattered, and praised mall staff for quickly cordoning off the area and sweeping up the fragments from the road and footpath.
''We haven't been able to determine what the failure has been,'' Dunedin City Council property manager Kevin Taylor said last night.
An investigation would begin today, and would include contacting installers and the glass manufacturer, he said.
He was glad no-one was hurt in the incident, ''with the veranda taking the hit ... prevented anyone down below wearing anything on their heads''.
The shattered facade was made of safety glass and featured an image of a building that had once occupied the site.
In April 2011, the ODT reported a wheelchair-bound man and his support worker were showered with falling glass fragments when a 2m-long roof panel exploded inside the mall.
''I have been informed we have had another failure of glass inside the mall, but the details of that I am not aware of,'' Mr Taylor said.
Following that incident, the council paid for protective film to be added under every glass ceiling pane in the shopping mall, at cost of $60,000.
The incident was blamed on nickel sulphide inclusion, which can occur during the manufacture of float glass that is later toughened.
Nickel contamination meant nickel sulphide crystals, formed during glass toughening, slowly reverting to a larger form and expanding to trigger shattering.
