Toronto fire crews are investigating the source of a carbon monoxide leak that sent one person to the hospital early Monday after an overnight emergency in Etobicoke.

Toronto Fire Services said crews were called to a home on Taysham Crescent, located in the Kipling Avenue and Finch Avenue West area, at approximately 1:49 a.m. for what was initially reported as a medical call.

When firefighters arrived, they detected elevated levels of carbon monoxide inside the residence. Paramedics transported one individual to the hospital in serious condition. Two other people were assessed at the scene but declined transport to the hospital.

Firefighters remained at the home alongside Enbridge Gas technicians through the early morning hours, working to identify the source of the leak and ensure the property was safe before allowing anyone back inside.

Carbon monoxide, an odourless and colourless gas, can cause severe illness or death when inhaled in high concentrations, often without warning.

TFS has not yet confirmed what caused the buildup, but officials routinely remind residents to ensure carbon monoxide alarms are installed and functioning on every floor of a home, particularly near sleeping areas.