PLAISTOW, N.H. — A problem with a furnace is being eyed as the likely cause of carbon monoxide poisoning that killed three people and sickened a fourth in a home in Plaistow on Tuesday.

State Fire Marshall J. William Degnan said the fourth victim was taken to Massachusetts General Hospital after firefighters were called to the Plaistow home at 11:30 a.m. His condition was not immediately released.

Degnan said the home had a carbon monoxide detector but it didn’t have batteries. He said the investigation is focused on the propane-fired furnace.

All the victims were adults. One woman and two men were unresponsive when emergency crews arrived, according to Plaistow fire officials.

He said the victims’ identities won’t be released until the family has been notified.

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