"Although poultry has historically been responsible for far more Salmonella infections, in the most recent years ... produce seems to be catching up," the Center for Science in the Public Interest (CSPI) said, calling for tougher federal food safety standards.

In fact, vegetables and fruits triggered 31 outbreaks from 2002 to 2003, compared with 29 for chicken and other poultry, according to the report.

Overall, contaminated tomatoes, sprouts and other produce made 28,315 people sick during 554 outbreaks from 1990 to 2003 -- 20 percent of all cases CSPI analyzed.

Chicken made 14,729 people sick in 476 outbreaks, and eggs were responsible for 10,847 illnesses from 329 outbreaks, according to the group.

"Pathogens can adhere to the rough surfaces of fruits and vegetables, so consumers should take precautions, such as washing produce under running water," the report said, adding people should "still eat plenty of produce."

Food-related infections cause a range of problems from discomfort to severe dehydration and death, but most problematic organisms can be killed when food is cooked long enough at high enough temperatures.

Not all people exposed to an outbreak get sick, but those who do can experience vomiting, diarrhea and fever, among other problems for about a week. Some experience no symptoms but can infect others.

The report found seafood was the largest cause of outbreaks but led to fewer illnesses than other foods. There have been 899 such outbreaks between 1990 and 2003, leading to 9,312 illnesses.

CSPI officials urged federal regulators to do more to protect the nation's food supply -- a job currently divided among at least 10 US agencies, including the Food and Drug Administration and the Department of Agriculture.

One large, independent agency would reduce coordination troubles, conflicting standards and other problems that make the government slow to act, the group said.

Other changes could be made in the meantime, it added.

"FDA should require growers to limit the use of manure to times and products where it poses no risk. And packers and shippers should mark packaging to ensure easy traceback when fruits and vegetables are implicated in an outbreak," said Caroline Smith DeWaal, CSPI's food safety director.