Damage to a York University window initially thought to be caused by a bullet may have been caused by a rock, Toronto police say.

Police tweeted shortly before noon Monday that they were investigating what appeared to be a bullet hole through a window at York University’s Scott Library.

They later determined that it wasn't caused by a bullet but instead by a bottle of some kind.

Const. David Hopkinson said investigators are still trying to determine when exactly the damage occurred.

No injuries have been reported.