Toronto fire crews are investigating a possible carbon monoxide leak at a midtown building that left one woman dead Tuesday morning.Emergency services were called to Wychwood Avenue in the St. Clair Avenue West and Bathurst Street area at approximately 9:13 a.m. after reports of a suspected leak. Toronto Fire says investigators are still working to determine the source.Toronto police confirmed to CityNews that the call was initially for a medical emergency. Paramedics attended the scene, but the woman was pronounced deceased.Police say Toronto Fire officials advised that there was a smell of natural gas inside the building and requested that Enbridge Gas attend and check the levels.Authorities stressed that the cause of death has not yet been specified. “[That] would have to be determined by the Coroner, as we don’t know if the deceased had pre-existing medical conditions,” a police spokesperson said.As a precaution, the building has been evacuated while crews assess the situation.