The Ronkonkoma Fire Department was alerted of a Chief's investigation for a Carbon monoxide detector activation at 1731 HRS. Upon arrival of 1st Assistant Chief Kevin Murray, it quickly became evident that this was more than just a routine investigation. Chief Murray noted high levels of Carbon monoxide present in the residence along with heavy smoke condition, at which point he reactivated for a full department response. On further investigation, it was discovered that there was active fire in the basement by the boiler, which was rapidly extinguished by the first due Engine crew and extensive ventilation was performed. All units were back in service at 1908 HRS with no reported injuries and the home along with its occupants were also unharmed.