1 How could investigators, who first pointed to tomatoes, now say other foods may be a cause?
After the first cases of salmonella saintpaul, a rare strain, were picked up in New Mexico and Texas in late May, studies done by state health departments and the Centers for Disease Control found a common denominator among those who fell ill: They had eaten tomatoes. "But the outbreak has continued, even though lots of people have stopped eating tomatoes," says Dr. Robert Tauxe, deputy director of the CDC's division of food-borne diseases. "So we've begun exploring the possibility that it was something in addition to tomatoes."

2 What other products are under suspicion?
While investigators won't disclose a full list of what else they're looking at, Tauxe says they are checking into salsa ingredients because, in cases where people fell ill, "often, the tomatoes were eaten in the form of salsa." Common ingredients include jalapeño and serrano peppers and cilantro.

3 So does this mean tomatoes are okay?
No. "Tomatoes are definitely not off the hook," Tauxe says. Initial case studies showed 80 percent of people who had contracted salmonella had eaten tomatoes—too high to be a coincidence, experts say. One complicating factor: Tomatoes from different farms are often mixed together and follow a complex distribution chain before they hit grocery store shelves or arrive at a restaurant. "It becomes very difficult to find your smoking gun," says Dr. James Gorny, produce food safety specialist at the University of California at Davis.

4 How do foods get contaminated with salmonella?
Water is the most common source. Sometimes, says food safety expert Dr. Doug Powell, associate professor at Kansas State University, livestock-contaminated water is used for irrigation or to rinse tomatoes. Birds also can be salmonella carriers, he says, "which can be problematic if they poop on a vegetable."

5 How serious is salmonella?
So far in the current outbreak, there have been no deaths and 189 hospitalizations. But some experts estimate that for each reported illness, another 20 people may have been stricken but have not come forward. Common symptoms include nausea, vomiting, fever, diarrhea and abdominal cramps, all of which can be potentially serious, even fatal, for children, seniors and those with weakened immune systems.

6 What should consumers do to stay safe?
Avoid raw red plum, red Roma and round red tomatoes unless you are confident they were grown in one of the FDA's "cleared" areas, listed on its Web site (www.fda.gov); safe choices include grape and cherry tomatoes and tomatoes with vines still attached. Canned and processed tomatoes are also safe—as is salsa in jars. Many retailers and restaurants now provide information about the source of their fresh tomatoes. A good rule of thumb: "If you don't know where it came from," says FDA spokesman Mike Herndon, "don't eat it."