West Hartford, CT – Three people were hospitalized Sunday morning after carbon monoxide filled their home, fire officials said.

Firefighters were called to 309 North Main St. at about 8:14 a.m. after a report of soot in the building, which houses a business and residential space.

Police and firefighters responded and firefighters discovered high levels of carbon monoxide, a colorless and odorless gas that is a byproduct of combustion of fossil fuels. Some of the CO levels firefighters detected were so high they could have endangered the lives of the four people in the building.

The people were helped out of the building and paramedics treated them. Three were taken to area hospitals.

The investigation into what caused the high levels of CO is underway and the heating system is suspected, West Hartford Fire Chief Greg H. Priest said.

He urged town residents to make sure they have functioning smoke and carbon monoxide detectors in their homes.