Federal health officials began warning consumers on June 3 to avoid raw red plum, red Roma and red round tomatoes, as well as products containing them, until the outbreak is contained. Consumers were advised Tuesday that cherry and grape tomatoes and those sold with the vine attached weren't likely to be tainted with salmonella.

Of the total reported thus far, 179 people first became ill after June 1, said Robert Tauxe, deputy director of CDC's foodborne disease division, in the conference call. More than 80 percent of them consumed fresh tomatoes, making that vegetable the prime suspect, he said.

FDA officials have said they believe the outbreak involves tomatoes grown in Mexico or Florida, and investigators are checking points along the distribution chain from those locations. Samples of tomatoes taken during the investigation have tested negative.

Tomatoes have been shipped from Mexico to Florida, combined with Florida tomatoes, and packaged together, complicating the FDA's investigation, Acheson said. In other cases, tomatoes were shipped from Florida to Mexico for packaging, and then shipped back to the U.S.

If the tomatoes are from locations listed as cleared on the FDA's Web site, the products are safe to eat. If they aren't on the list or vendors don't know where they're from, the tomatoes shouldn't be consumed, the FDA says.

Most people infected with salmonella have diarrhea, fever and cramping for four to seven days and recover without treatment. The people most susceptible to hospitalization or death are infants, the elderly and people with impaired immune systems.