Carmel, IN – Authorities say six people were taken to a hospital after carbon monoxide from a running SUV filled an apartment building in suburban Indianapolis.

Firefighters reported finding carbon monoxide in all seven units of the Legacy Towns and Flats building in Carmel late Wednesday.

Fire Capt. Kurt Weddington tells WTHR-TV that 13 people were evacuated from the building, with seven of them declining medical treatment after being checked for carbon monoxide exposure.

Weddington says the SUV was parked inside a closed garage on the lower level and that carbon monoxide spread throughout the building. Near-fatal levels of the gas were found in some apartments.

Weddington says investigators were waiting for the SUV’s owner to be released from the hospital to determine why the vehicle was left running.