McKINNEY, Texas -- Emergency workers treated seven people overcome by carbon monoxide fumes in McKinney early Wednesday.

Firefighters suspect a faulty heating unit may have poisoned the family's home on North West Street.

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The family woke up feeling nauseous Wednesday morning. They thought it was food poisoning, but when one of them fainted, they called 911.

Rosa Martinez, her husband and five other family members were suffering from carbon monoxide poisoning, apparently caused by a faulty furnace.

They wound up in a hospital, and the father remained hospitalized overnight.

To avoid problems with carbon monoxide this winter, firefighters recommend people keep their furnace in good working order and have carbon monoxide detectors installed in their home.