The warning, which follows a potential outbreak of E. coli O157:H7 in Minnesota, could significantly dent consumer confidence in a highly lucrative sector of the convenience food market.
Pre-washed salads, which can be eaten without further washing according to the US Food and Drug Administration (FDA), encapsulate in many ways what modern consumers want; convenience, nutrition and safety. Unsurprisingly, sales topped $2.3 billion last year, according to market analyst ACNielsen.
The product has even been credited with boosting consumption of fruits and vegetables by making them easier and more attractive.
But the discovery of a potential food poisoning outbreak could change all that. Bacteria that cause food-borne illness can be destroyed by cooking, but most salads are served raw.
This is the latest case of fruit and vegetable products to have been linked with a food poisoning outbreak. Dried basil contaminated with Salmonella was at the center of a major product recall in California earlier this summer, resulting in the recall of all potentially affected products.
Paradoxically however, these recalls could show that the FDA is on the ball when it comes to protecting the public from food poisoning. Procedures have certainly been tightened up, and the agency is confident that any threat - whether accidental or deliberate - will not escape detection.
As result, the incidence of E. coli O157 infections decreased 42 percent from 1996 to 2004. Campylobacter infections fell 31 percent, cryptosporidium dropped 40 percent, and yersinia decreased 45 percent.
And last week, a final ruling requiring all manufacturers to register with the Food and Drug Administration (FDA) was approved. This is one of five regulations to have been issued by the agency in order to implement the Bioterrorism Act.
"This rule is one of our critical tools for safeguarding the American food supply," said acting FDA commissioner Andrew C. von Eschenbach.
"By finalizing this rule, we now have another important safeguard in our ongoing efforts to make sure that human and animal foods are protected from a deliberate or accidental act of contamination."
The new law will allow the FDA to quickly locate food processors in the event of deliberate or accidental contamination of the food supply. Except for specific exemptions, the registration requirements apply to all facilities that manufacture, process, pack, or hold food, including animal feed, dietary supplements, infant formula, beverages and food additives.
Other rules issued under the authority of the Bioterrorism Act of 2002 include the requirement of food firms to keep records that would allow FDA to conduct an effective and efficient investigation to protect the US human food and animal feed supply.
The agency says that the speed at which these "one-step forward, one-step back" records can be accessed in case of potential food contamination is critical in diminishing the impact on consumers. If companies are unable to trace and isolate the source of a possible food contamination problem within 24 to 48 hours, the potential of serious damage increases exponentially.
The FDA and the Minnesota Department of Health are now looking for the source of the latest outbreak. The three recalled salad mixes - Classic Romaine, American Blend and Greener Selection - contained three common ingredients: romaine lettuce, carrots and red cabbage.
"Given the severity of this illness, FDA believes an urgent warning to consumers is needed," said Dr. Robert Brackett, director of the FDA's Center for Food Safety and Applied Nutrition.
"FDA is working closely with the US Centers for Disease Control and Prevention (CDC) and our state partners to further identify the source of the problem and its scope."
Dole Fresh Vegetables, a division of Dole Food Company, has announced that it intends to cooperate with the FDA and the Minnesota and California State Departments of Health regarding the investigation and recall.
"Our over riding concern is for consumer safety," said Eric Schwartz, president, Dole Fresh Vegetables. "We are working with the US-FDA, the Minnesota Department of Health and the California Department of Health Services to determine the source of the contamination."