Fourteen Boy Scouts and one adult who attended a popular camp in Virginia's Blue Ridge Mountains contracted an E. coli infection from a source public health officials have yet to identify.

Nine of 50 to 60 scouts and staff who reported being ill have been hospitalized, the Virginia Department of Health said Friday. Citing privacy concerns, they could not provide their conditions.

Most of the scouts are from northern Virginia, and one of the confirmed cases involves a Maryland adult.

Officials are trying to determine the source of the outbreak, which is most commonly caused by undercooked contaminated ground beef.

The department began receiving reports Sunday when boys from about 70 troops returned home after a week at the Goshen Scout Reservation in Rockbridge County.

Nearly 1,500 scouts and adult leaders and 200 staff were at the camp from July 20-26, the National Capital Area Council of the Boy Scouts of America said in a statement.

Department officials have since visited the 4,000-acre camp, located between Lexington and Staunton in western Virginia, and found no obvious sources of the outbreak. The camp includes Lake Merriweather.

"We're trying to recreate the past," Seth Levine, a state epidemiologist, said of the investigation. He said it was too early to link the outbreak to ground beef or any other source.

Not everyone exposed to E. coli becomes ill, Levine said. Those who do commonly suffer from stomach cramps, watery bloody diarrhea, and fever and chills. In severe cases, the infection can damage organs such as kidneys.

Public health officials who visited the camp examined its food handling and storage practices and recommended changes, said Robert Hicks, director of the office of environmental health services.

In a statement posted Friday on the council's Web site, executive Alan Lambert said he instructed unit leaders to contact boys and adults who attended the camp and advised them to seek medical treatment if they show any signs of the infection.

E. coli0157, which sickened the 15, is the most common form of the infection. Possible sources also include unwashed greens, swimming in contaminated water, and food fouled by preparers who haven't washed their hands.

The federal Centers for Disease Control and Prevention estimates that E. coli sickens about 73,000 people and kills 61 each year in the United States. Most of those who die have weak immune systems, such as the elderly or very young.