Roads in the Bloor Street East and Sherbourne Street area are closed as Toronto police conduct an investigation.
Police say they received a 9-1-1 call shortly before 3 p.m. Tuesday.
Officers on scene told 680 NEWS they were looking into a bomb threat but did not specify exactly where. Employees from a nearby building said they had been asked to evacuate, but police did not confirm any evacuations.
No injuries have been reported.
Bloor is closed between Sherbourne and Mt. Pleasant and drivers are being asked to take alternate routes.
No further details are available at this time.