Tomato-borne salmonella infections give Americans a hard time, with the U.S. Centers for Disease Control and Prevention announcing more cases with each day passing by.

There were nine states the first time the U.S. health authorities announced the outbreak at the beginning of this month. Salmonella infections in the U.S. were linked to red plum, red Roma or round red tomatoes, the FDA said in a statement on its Web site.

Three days later, the number of states affected by salmonella reached 16, while last Friday, the Food and Drug Administration released a statement saying five more states had reported salmonella cases. Overall, 228 people were infected, 25 of them needing hospitalization.

On Monday, the CDC said the number of people infected by salmonella has grown to 277 from 28 states and the District of Columbia. The number of people needing hospitalization has also raised reaching 43.

The source of infection has not been found yet, but the FDA believes the salmonella contamination likely started in Florida or Mexico, the two major tomato-producing areas.

On Saturday, the FDA eliminated New Mexico, Indiana and Baja California as the origin of the outbreak. By late Monday, Connecticut and Washington D.C. were also eliminated from the list of states believed to be the source of salmonella infection. Overall, 38 states were excluded, including California.

Dr. David Acheson of the CDC said nine people became infected after eating tomatoes from the same company, although he did not say where the company was located or whether it was a grocery store or a restaurant. This is “the most fruitful lead to date,” which could help health officials trace the source of the outbreak, the Los Angeles Times reports.

Until further information is available, people should consume only cherry tomatoes, grape tomatoes, or tomatoes grown at home, which were declared safe. Also, they should follow the health officials’ advice on how to process tomatoes.