The historic Peacock Hotel in the Junction was evacuated Monday after a partial collapse was reported at the rear of the building.
Police and firefighters responded to a call in the Dundas and Dupont Streets area around 1:30 p.m.
No injuries have been reported.
Two TTC buses were ordered to shelter those evacuated.
It is unknown when exactly the collapse occurred and building inspectors have been called in to assess the integrity of the structure.
Toronto police K-9 units are on scene to search the rubble behind the building to locate any potential victims.
The Peacock Hotel was established sometime in the late 1820s or early 1830s and was a famous resting place in Toronto for travelers and their horses on their way to other settlements. It is also a notable location in the Mackenzie Rebellion, outside which William Lyon Mackenzie robbed the Royal Mail in 1837.