WASHINGTON — More than 1,000 people now have become ill from salmonella initially linked to raw tomatoes, a sobering milestone yesterday that makes this the worst foodborne outbreak in at least a decade. Adding to the confusion, the government is warning certain people to avoid types of hot peppers, too.

Certain raw tomatoes — red round, plum, and Roma — remain a chief suspect and the government stressed again yesterday that all consumers should avoid them unless they were harvested in areas cleared of suspicion.

But people at highest risk of severe illness from salmonella also should not eat raw jalapeno and serrano peppers, the Centers for Disease Control and Prevention urged yesterday. The most vulnerable are the elderly, people with weak immune systems, and infants.

Raw jalapenos caused some of the illnesses, conclude CDC investigations of two clusters of sick people who ate at the same restaurant or catered event.

But jalapenos cannot be the sole culprit — because many of the ill insist they didn’t eat hot peppers or foods like salsa that contain them, the food safety chief of the CDC, Dr. Robert Tauxe, told the Associated Press. As for serrano peppers, that was included in the warning because they’re difficult for consumers to tell apart.