Temporary scaffolding will go up around the Festival Tower condominiums at the TIFF Bell Lightbox just weeks before the start of its international film festival.   

It's an effort to protect people from falling glass.  

On Tuesday night, pieces of tempered glass fell from a 27th floor balcony onto John Street just north of King Street West.  No one was injured.

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The missing glass pane can be seen about halfway up the tower. ((Andrew Lupton/CBC))

"We still don't know as to why this one in particular would have failed," said Tom Dutton, a senior vice-president with Daniels Corporation, the condo developer.

Three weeks ago a piece of glass broke free from the same building.  

Dutton says in that instance the metal balcony railing expanded in the heat placing too much pressure on the glass.

In the most recent incident Dutton thinks something may have hit the panel. 

But until they know exactly what happened and how to prevent it, the developer is taking precautions.

"We're going to be erecting temporary scaffolding along the sidewalk on John Street," Dutton said.  

"The way the balcony has been designed, it's in accordance with all the codes and practice with construction technique but for some reason we seem to have this problem with the tempered glass is letting go," said Dutton.

It's the second time  this week that shattered glass from a condo building has forced road closures in downtown Toronto. 

Earlier this week a condo on Grosvenor Street also lost balcony glass.  There were no injuries in the incident.

Barry Fenton, of Lanterra Developments, said the company has decided "to take down the balconies and repair them, replace them entirely."

Local city councillor Adam Vaughan says the provincial building codes and practices might need another look.

"The glass balconies are tested for pushing against the balconies," said Vaughan.  "What they are not stress tested for, apparently, is the wind shear."

Vaughan says experts feel provincial building codes should be revised.