Toronto police and fire officials are warning residents in west-end Toronto to stay indoors after acid was released into the air.

Toronto Fire Capt. Michael Westwood says a combination of hydrochloric and sulphuric acid was mixed and released into the air, creating a fog that can be irritating if inhaled.

Const. Caroline De Kloet says police were alerted to the incident shortly before 10:00 a.m. when a resident walked outside, witnessed a cloud of smoke and began coughing.

Officials have no word as to the source or scope of the acid release in the Bloor Street and Lansdowne Avenue area, but say there are no reports of injuries.

Police and fire services are on scene assessing the situation and road closures are pending.

De Kloet says residents in the area are urged to remain inside with their doors and windows shut to prevent ingesting potentially hazardous fumes.