According to Safeway, US supermarket chain, some of its ground beef may be tainted with Salmonella as the company was informed of the potential threat by the U.S. Department of Agriculture.

According to a company release, the ground beef in question would have entered the supply chain between September 19 and November 5. The products were sold in five western states - Arizona, California, Hawaii, Nevada and New Mexico.

Safeway says as far as it knows the investigation into the source of the contamination is still underway. To date investigators have been unable to pin down the source.

Safeway officials stress the salmonella threat is limited to frozen ground beef products. Fresh ground beef is not affected. The USDA, however, said the warning applies to fresh ground beef products that consumers may still have in their freezers.

The grocer said frozen ground beef purchased between September 19 and November 5 should be discarded.

The USDA said the alert follows investigations by the California, Arizona, Idaho and Nevada public health departments. It said 38 illnesses had been reported in those states.

The illnesses were linked through the epidemiological investigation by their rare PFGE pattern found in PulseNet, a database maintained by the Centers for Disease Control and Prevention.

The USDA said it could not identify specific establishments, lots and products that would be subject to a recall, and said there is no reason to believe the contaminated beef products are still available in stores.

This particular strain of Salmonella is resistant to many commonly prescribed drugs, which can increase the risk of hospitalization or possible treatment failure in infected individuals.

Consumption of food contaminated with Salmonella can cause salmonellosis, one of the most common bacterial food borne illnesses. Salmonella infections can be life-threatening, especially to those with weak immune systems, such as infants, the elderly and persons with HIV infection or undergoing chemotherapy. The most common manifestations of salmonellosis 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.