Baltimore, MD- A friend pounded on the door of the second-floor apartment of the Guilford Avenue rowhouse, waiting for the family matriarch to emerge for their daily walk. It was 7:30 Tuesday morning, and when there was no answer, the friend gave up and went on her way.

Hours later, police and firefighters responding to a call for people sick on the second and third floors of the three-story red brick house in the 1700 block of Guilford Ave. found two adults dead and three others, including a child, unconscious, apparently the Baltimore area’s latest victims of carbon monoxide poisoning.

Fire officials said all five are related. The survivors were rushed to the hyperbaric chamber at Maryland Shock Trauma Center, where authorities said they were in serious condition. Authorities had not released their names or ages Tuesday evening.