Toronto police and fire responded to the call on Saturday afternoon at 4091 Sheppard Ave E, near Kennedy, and discovered a makeshift lab set up in an 18th-floor unit. Officials have since dismantled the setup.
Seven floors in the building had to be cleared, displacing some 50 residents in the condo. Police said the residents were loaded onto buses and moved to nearby hotels for the evening.
Police removed several unidentified chemicals and have deemed the condo safe for residents to return to on Sunday morning.
The chemical smell reported by neighbours was described as a strong "chlorine or bromine smell," police said in a release.
Officials say it's too early to determine what the chemists may have been trying to manufacture in the lab, though investigators believe the operation was drug-related.