Firefighters were called to a fire in an apartment at 140 Langarth Street in south London around 8:30 a.m. on Wednesday.

A woman was pulled from the building and CPR was performed on site before she was transported to hospital.

London police say she remains in critical condition.

A resident who lives across the hall from the apartment where the fire broke out tells CTV News she saw a lot of black smoke.

Fire officials say there were working smoke alarms in the building.

A London Transit bus was sent to the scene to keep residents warm. About 22 people live in the building.

An investigation is underway involving London police, London fire and the Ontario Fire Marshal's Office.

This is not the first time there has been a fire in the building.

A blaze in June 2015 left 39-year-old Christopher Joseph Manuel dead.

That fire was not suspicious.