CLEVELAND (AP) _ A bird's nest in a furnace flue forced carbon monoxide into a house and killed the two adults and three children inside, investigators said Friday.

The nest was found Friday inside a flue leading from the furnace to the house's roof. Carbon monoxide is supposed to be emitted out of the chimney, but investigators said the flue was at least partially obstructed.

The house had a hot water heating system with a gas-fired boiler, said Assistant Fire Chief David Glauner.

The victims were found Thursday night by police who forced open a door of the house. A neighbor had called police after trying to reach the family for two days.

Blood tests confirmed that the five suffocated from carbon monoxide, said Robert Challener, deputy coroner for Cuyahoga County. A dog also was killed by the colorless, odorless gas.

The coroner's office identified the victims as John Reed, 40; his children, Kristen Reed, 13; Megan Reed, 11, and John Reed Jr., 10; and Karen Smith, 45, a family friend.