(Adds details of outbreak, company response)
By Ros Krasny
WASHINGTON, Oct 7 (Reuters) - Hundreds of people in 18 states have become sick from a salmonella outbreak linked to raw chicken products made at three California plants owned by Foster Farms, the U.S. Department of Agriculture said on Monday.
"The outbreak is continuing," USDA's Food Safety and Inspection Service said in a statement.
An estimated 278 illnesses, mostly in California, were caused by strains of Salmonella Heidelberg. The chicken products were distributed mostly to retail outlets in California, Oregon and Washington state, USDA said.
The illnesses were linked to Foster Farms brand chicken through epidemiologic, laboratory and traceback investigations conducted by local, state and federal officials.
In a statement, Livingston, California-based Foster Farms said it was working with authorities to reduce the incidence of Salmonella Heidelberg on raw chicken products.
No recall is in effect, the privately owned company added.
The Centers for Disease Control and Prevention is partnering with state health departments to monitor the outbreak while the Food Safety and Inspection Service (FSIS) continues its investigation, USDA said.
"In addition to collaborating with FSIS and CDC, the company has retained national experts in epidemiology and food safety technology to assess current practices and identify opportunities for further improvement," Foster Farms President Ron Foster said in a statement.
Salmonella Heidelberg is the third most common strain of the Salmonella pathogen, which can result in foodborne illness if not destroyed by the heat of proper cooking.
The most common symptoms of salmonella infection are diarrhea, abdominal cramps and fever within eight to 72 hours. Additional symptoms may be chills, headache, nausea and vomiting that can last up to seven days.
FSIS is one of the arms of USDA that continues to work during the federal government shutdown, but with reduced staffing. Meat, poultry and processed egg inspection activities have been maintained.
Raw products from the facilities bear one of the following numbers inside a USDA mark of inspection or elsewhere on the package: P6137, P6137A or P7632.
(Reporting by Ros Krasny; Editing by Lisa Shumaker)