Richard Irwin | The Baltimore Sun

Nine people, including seven children, were treated at two separate medical facilities Sunday afternoon for the nonlife-threatening effects of a natural gas leak in a Northeast Baltimore apartment, said a spokesman for the city Fire Department. Hours later, three others were treated for another carbon monoxide leak in Howard County.

Chief Kevin Cartwright said when firefighters and medics arrived at a two-story apartment in the 6900 block of McClean Blvd. near Perring Parkway shortly after 3 p.m., they found seven children and two adults complaining of feeling ill.

Cartwright said the children, the youngest 18 months, were taken by ambulances to the University of Maryland Medical Center and the adults to Maryland Shock Trauma Center. He said firefighters and a Baltimore Gas and Electric Co. crew traced the leaking carbon monoxide to a malfunctioning gas-operated water heater on the first floor and shut it down.

Fans were used to ventilate the apartment. Cartwright said low levels of the gas also were found in two adjacent vacant apartments.

The apartment complex is owned by Sawyer Realty Holdings LLC, a College Park-based company that manages dozens of other housing communities in Baltimore and Prince George's counties. One complex, Cove Village in Essex, has a history of carbon monoxide problems, including two incidents that sent eight people to the hospital last month.

In Howard County, firefighters responded Monday morning to a call for carbon monoxide in the 10300 block of Twin Rivers Road that sent three people to Howard County General Hospital. Fire officials said the leak displaced a family of five, and crews were attempting to find the source of the leak.