An outbreak of salmonella has sickened at least 388 people across the United States, including 67 who required hospitalization, health officials said.
The US Centers for Disease Control and Prevention (CDC) so far has been unable to pinpoint a source for the outbreak, which was first detected in September and which now has spread to 42 states, according to agency spokesman Tom Skinner.
Two federal agencies responsible for the oversight of food products, the US Department of Agriculture and the US Food and Drug Administration, also are taking part in efforts to track the source of the scourge.
The CDC, based in Atlanta, Georgia, has said that salmonella, which can be fatal, especially in children, remains a "major public health problem in the United States." Eggs and cheese are among the foods most likely to be contaminated, the agency said.
The salmonella bacterium is spread most often by the consumption of food contaminated by animal fecal matter, according to health experts.
The microbe usually flourishes within the intestinal tracts of fowl and mammals.
An estimated 1.4 million human salmonella infections occur each year, causing about 15,000 hospitalizations and 400 deaths, according to the CDC.