The incident occurred at the St Kilda Road landmark - now known as NGV International - on Tuesday last week.As a safety precaution, staff began closing off public access to major displays within hours of discovering the damage.
But it was not until yesterday - after inquiries from The Age - that the gallery released a statement detailing what had happened and confirming the closure of seven of its 30 gallery spaces.
The statement said a vertical pane of glass from the top of the gallery's Coles Court had shattered, with falling fragments causing "cosmetic" damage to a glass rampway.
Areas accessed through the Coles and Murdoch courts had been closed for safety reasons.
The gallery said the closures had been prolonged because engineers were not available in the Christmas-New Year period. Two groups of engineers went through the building yesterday and were due to present a report this morning.
It was not known when the spaces would reopen.
Among the areas closed is one devoted to monumental installations by four leading overseas artists who came to Melbourne for the gallery's relaunch. Also closed is a multi-media survey of the career of Italian architect and designer Mario Bellini, the principal architect for the building's $168 million redevelopment.
Other areas not open are those displaying Greek and Roman antiquities, oceanic art, prints and drawings, Asian art, 16th to 17th-century painting and sculpture, international 20th-century art and contemporary art.
The mezzanine spaces on the second floor are also shut.
The St Kilda Road gallery is not alone among recent big public building projects in Melbourne to have suffered broken glass problems. At the $290 million Melbourne Museum complex in Carlton, there were five incidents of shattered glass within 12 months of its opening in 2000.
NGV International has attracted big crowds since its much-celebrated reopening on December 4. In the first four days of business there were 56,000 visitors.
The original gallery was designed by Sir Roy Grounds and completed in 1968. The former Kennett government commissioned Mr Bellini and Melbourne firm Metier 3 to give it an architectural makeover in 1996. It was closed for 4½ years.