Two panes of glass fell from the RBC Centre at 155 Wellington St. Monday evening.
The first pane fell at about 7 p.m., with the second shattering on the ground shortly after police arrived at the building.
Police said the panes fell from the 31st and 11th floors.
No one was injured, but streets and sidewalks were closed as a precaution while police investigated.
The street closure affected Simcoe Street between Wellington and Front streets.
Contractors were called in to fix the broken panels. It's not yet known what caused the glass to fall.
This isn't the first incident of falling glass in the downtown core.
On March 26, the area around an office tower on 180 Queen St. W. was closed after a piece of glass fell from the 16th floor.
Two days before that, strong winds blew glass from the Trump Tower at the intersection of Bay and Adelaide streets.
