WA, D.C. – NBC4 – Six members of a northwest Washington family have been hospitalized with carbon monoxide poisoning.

Police say the family lives in the 1300 block of Perry Place N.W.

Officials say a member of the family turned the furnace on about 7 p.m. Sunday night, but then around midnight a female started suffering from a headache, complained of nausea and was disoriented.

When other family members started suffering the same symptoms, police said they realized they may be dealing with carbon monoxide and called authorities.

Four Metropolitan Police officers were the first to arrive and assisted with evacuating 11 people from the house, six of whom were unconscious.

Everyone was taken to the hospital including the four officers who assisted with the evacuations. Six members were kept for observation.

Carbon monoxide is a colorless, odorless gas that can cause sudden illness and death. Officials say furnaces should be checked at least once a year.