The US government has added hot peppers to its salmonella danger list as new figures showed more than 1,000 people were ill from the bug initially linked to raw tomatoes.
The salmonella figures make it the country's worst food-borne outbreak in at least a decade.
The government also warned vulnerable people to avoid hot peppers.
Certain raw tomatoes - red round, plum and Roma - remain a chief suspect, and the government stressed that all consumers should avoid them unless they were harvested in areas cleared of suspicion.
People at the highest risk of severe illness from salmonella should also not eat raw jalapeno and serrano peppers, the Centres for Disease Control and Prevention urged. The most vulnerable are the elderly, people with weak immune systems and infants.
Raw jalapenos caused some of the illnesses, CDC investigations of two groups of sick people who ate at the same restaurant or catered event concluded.
But jalapenos cannot be the sole culprit; many of the sick insisted they did not eat hot peppers or foods like salsa that contained them, CDC food safety chief Dr Robert Tauxe said.
Serrano peppers were included in the warning because they were difficult for consumers to tell apart.
In some clusters of illnesses, jalapenos "simply were not on the menu", Dr Tauxe said. "We are quite sure that neither tomatoes nor jalapenos explain the entire outbreak at this point. ... We're presuming that both of them have caused illness."
That has Food and Drug Administration inspectors looking hard for farms that may have grown tomatoes in the past three or four months and then switched to pepper harvesting, or for distribution centres that handled both types of produce.