Investigators were today trying to find out why part of the stone parapet of the building in Baliol Street collapsed.
Eyewitnesses described "chaos" as residents were evacuated from their homes.
As fears grew of a possible gas explosion, police cleared the buildings and closed the street, near Woodlands Road, in Glasgow's West End.
Families - including pets -had to flee their homes after being told to collect their belongings and move out immediately.
Emergency services were called to reports of "roof collapse" at around 1.40pm yesterday, but local residents and shopkeepers then noticed an "overpowering" smell of gas.
It is not known if the incident was caused by gas, or if the smell was a result of the damage to the building and street below caused by the falling stonework.
As a precaution, all properties between 15 and 19 Baliol Street were emptied of residents.
One evacuated resident, who did not wish to be named, said: "I was asleep and woke up when I heard this loud crash.
"I knew it didn't sound good, but I can't believe the roof is gone.
"We were told it's gas and that's why we can't get back in yet.
"We have no idea when we'll be able to go home."
No one was injured in the incident.
Debris and broken masonry could be seen on the street outside the properties.
A woman, who lives just off Baliol Street, said: "Everyone came out to see what was going on - there was a strong smell of gas.
"I couldn't believe how much damage has been done.
"We're lucky no one was walking in or out of the building when it happened."
Fire crews, including specialists officers, were at the scene assessing the damage and ensuring the building was safe.
Investigators are today working to establish what caused the parapet to collapse.