A malfunctioning natural-gas heating system is suspected in the deaths of two members of a Cheltenham family and the hospitalization of a third, likely victims of carbon-monoxide poisoning, Police Chief John Norris said yesterday.

The victims were not named, but Norris identified the two who died as a 50-year-old man and his 15-year-old son. The man's 44-year-old wife, stepmother of the youth, was admitted to Elkins Park Hospital. A second son was not home at the time, the chief said.

Tuesday afternoon, the Cheltenham School District asked police to investigate after the 15-year-old had missed a second day of school without notice, Norris said. Peco and the county Fire Marshal's Office reported the stack on the heating system was clogged with soot. - Jeff Price