A Toronto councillor says it's not clear what caused glass to fall from a downtown luxury hotel on three separate occasions this year.

Police were called to the Shangri-La Hotel, which is located on University Ave near Adelaide Street West, early Sunday.

No one was hurt, but this is the third such incident this year.

In September, one person was injured after being hit by a piece of falling glass. Glass also fell from the building in January.

Coun. Adam Vaughan said it is "concerning" that the city and hotel still haven’t figured out what is going on.

"We haven’t figured out why the last piece fell and it doesn’t appear to be a manufacturing problem, it doesn’t appear to be an anchoring issue. It’s a bit of a mystery," he said in an interview with CBC News on Sunday.

"And the owner of the building [and] the city, we’re all inspecting, but we’re not coming up with answers and that makes us very worried."

The hotel says it is investigating the incident and trying to determine the cause.

It's not the only downtown building where falling glass has been a problem. Last year, similar incidents happened at the RBC Centre, the Trump Tower and the Festival Tower condominiums at the TIFF Bell Lightbox.