Parts of a roof from a downtown Toronto office building collapsed Wednesday morning, sending large chunks of debris crashing to the ground and temporarily blocking traffic.

Police responded to a call at University Avenue at College Street after the partial roof collapse at about 10:30 a.m.

The building at 700 University Ave. is home to the Ontario Power Generation headquarters and a bank and is just south of the Ontario legislature at Queen's Park.

Debris fell from the overhang of the building, dropping about 10 metres to the walkway below. Police said pieces of drywall also cracked off columns in an area of the building currently under construction.

Kenneth Kowlessar, who captured the incident on his cellular phone, said he heard a creaking and then a crash.

While pieces of drywall did crash to the sidewalk, no injuries were reported. Building managers said the area had been cordoned off earlier after structural damage was found.

"Earlier today some of our staff on a regular maintenance check had noticed that there were some structural issues with that part so we took the precaution to close it off and perhaps because of the high winds or whatever it has come down this morning," said OPG spokesman Ted Gruetzner.

"Fortunately nobody got hurt but we are going to investigate, find out what happened to it and get this cleaned up as soon as possible."

Although safety officials determined that employees in the building were not at risk, Gruetzner said The Bank of Montreal decided to remove its employees from the site.

"The Bank of Montreal, which is right where it fell, has taken the decision to send their staff home or at least keep them away for the time being, but our staff and the other tenants in the building are all here at work and the shops are open. It is business as usual."

Toronto fire crews cleared the scene shortly before noon, while police diverted pedestrians.

Large garbage bins were brought in to haul away the shattered drywall.

Officials said engineers will need to check the integrity of the structure before opening the area to pedestrians.

With a report from CTV Toronto's Tamara Cherry