Eight more cases of people becoming infected with salmonella traced to dry dog food have been identified, US health officials said on 6 November, according to HealthDay News.

The outbreak, which started in 2006, marks the first time that dry dog food has been confirmed as a source of the bacterial infection in people.

As of 31 October, 79 cases of Salmonella Schwarzengrund had been reported in 21 states. Most of the cases involved children 2 years old and younger, according to the federal Centers for Disease Control and Prevention.

"We have been following an outbreak of illness due to a specific strain of salmonella. And in 2007, we linked those human illnesses with contaminated pet food produced at one Pennsylvania pet food plant," said report co-author Dr Casey Barton Behravesh, a CDC epidemiologist. "In 2008, we have identified eight additional cases."

The dog food has been traced to a Mars Petcare US plant in Everson, Pennsylvania. On 12 September, the company announced a recall of approximately 23,109 tons of dry dog and cat food sold under 105 brand names. The plant is now closed, the CDC said.

Despite the recall and the plant closing, Dr Barton Behravesh said the threat of more infections exists. "The issue is that since dry pet food has a one-year shelf life, it is possible that contaminated products from even our 2007 recall could still be in the homes of ill persons and could lead to additional illness," she said.