AUGUSTA — The Maine Center for Disease Control and Prevention issued a warning about carbon monoxide poisoning Thursday, saying seven Mainers have been sent to a hospital with carbon monoxide poisoning since November.

No fatalities have been reported.

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The state CDC urged Mainers to heat their homes safely and be extremely cautious while working on engines in garages.

Malfunctioning home heating sources were the cause of five of the recent poisonings and two people were poisoned while working in their garages, one from exhaust that built up while working on a car engine and the other from space heaters.

In Maine, about 75 percent of all reported cases of carbon monoxide poisoning occur between November and March, the agency said.

Anything that burns fuel, such as an oil or propane boiler or wood stove, produces carbon monoxide. When these appliances are not properly maintained or vented, carbon monoxide can build up inside a home without anyone noticing.

In another recent event, a carbon monoxide detector alerted a family to the presence of the poisonous gas coming from a wood stove. The family got out safely. In the  overwhelming majority of poisonings reported to the state agency, there were no carbon monoxide detectors present.