Tomato growers and sellers have estimated their losses at $100 million so far, while critics in Congress have complained about delays in identifying the source of the outbreak.
There have been repeated calls for an overhaul of the nation's food safety system and the implementation of better methods for tracking produce.
"I've never seen a situation like this," William Marler, a Seattle lawyer who litigates food-borne illness claims, said in a recent interview.
A mistaken focus on tomatoes would be a "black eye" for investigators, he said, while acknowledging that produce investigations are difficult.
Jalapenos are grown mostly in Mexico and, to a lesser extent, in California, Florida and Texas. At the time the outbreak began, Mexico would have been the main supplier but Texas farms would also have been harvesting, said James Ditmore, international marketing specialist at the New Mexico Department of Agriculture.
A 2003 study found that one salmonella strain grew at higher rates on peppers compared with other fresh produce, but the spicy peppers haven't been implicated in many outbreaks. Unlike leafy greens, jalapenos grow well above ground, limiting several normal causes of contamination, food scientists say.
Because jalapenos have a long shelf life - they can be stored in refrigerators for weeks - it's possible that a consumer or restaurant may still have a tainted jalapeno that can be tested for salmonella, food scientists say.
Since people began experiencing fever, diarrhea and abdominal cramps in April, the government has confirmed 1,017 cases of Salmonella saintpaul, including 29 in Maryland.
More than 200 people have been hospitalized.
In issuing a new warning about jalapeno and serrano peppers, officials said they were limiting their caution to the people most vulnerable to infection, though that could change as the investigation evolves.
Officials are still warning consumers to avoid eating raw red plum, red Roma and red round tomatoes unless they came from cleared regions, such as Maryland and more than 40 other states.
The new warning doesn't apply to salsa, even though significant numbers of the infected ate salsa at Mexican restaurants.
Tomatoes and raw jalapeno peppers are key ingredients in salsa.
Though some state health officials say it's unlikely that tomatoes are responsible, federal officials said again that they couldn't rule out tomatoes and implicate jalapenos as the lone cause.
"There is plausible evidence it could be both products," Tauxe said.
jonathan.rockoff@baltsun.com
FDA WARNINGS
The FDA has issued a new, expanded warning in response to the Salmonella saintpaul outbreak. Here are the warnings currently in effect: * JALAPENO PEPPERS: Infants, the elderly and those with impaired immune systems should avoid eating raw jalapeno peppers. TOMATOES: Consumers should avoid red Roma, plum and round red tomatoes unless they come from a source not linked to the outbreak. Maryland and more than 40 other states have not been linked to the outbreak (for a complete list see http://www.fda.gov/oc/opacom/hottopics/t omatoes.html#outbreak). Cherry tomatoes, grape tomatoes and tomatoes with the vine attached have not been linked to the outbreak.
Source: U.S. Food and Drug Administration
