WATERLOO, Iowa (AP) — Authorities say four adults and a toddler have been treated for carbon monoxide poisoning in Waterloo.

Firefighters found a woman unconscious in a doorway at the residence Wednesday night, and the rest of the occupants were out of the house and conscious.

Fire Battalion Chief Marty Freshwater says a gas-powered generator placed in a laundry room by the back door was supplying electrical power to the house and had been operating for about 30 minutes. Freshwater says the occupants mistakenly thought leaving a window open on the storm door would provide enough ventilation.

The occupants called 911 for help around 11 p.m. when they became sick at the same time.

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