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Salmonella spreading rapidly across 19 states: Spicy tuna rolls to blame?

Smart choice: Sushi Why it's healthy: Sushi is a low-fat food containing bite-size amounts of lean protein, carbs, and even vegetables. Choose veggie sushi for a light snack or a salmon roll for something more filling. Calories: At around 130 calories for a cucumber or salmon roll, sushi is a far better snacking option than a 1,200-calorie-plus bag of peanuts.More from Best and Worst Hot Dogs iStockphoto

(CBS/AP) - The government is investigating sushi as a possible culprit behind a salmonella outbreak that has sickened 90 people across 19 states and Washington D.C.

A memo from the Food and Drug Administration said the outbreak is "rapid and expanding in number of cases," with seven hospitalizations reported. No deaths have been reported to date.

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The investigators are reportedly honing in on spicy tuna rolls it calls "highly suspect."

Reports of the foodborne illness have mainly come from the eastern seaboard and Gulf Coast, though cases have been reported as far west as Missouri and Texas. Investigators are focusing on six clusters of restaurants in Texas, Wisconsin, Maryland, Rhode Island and Connecticut.

Symptoms of salmonella include diarrhea, abdominal cramps and fever within eight to 72 hours of eating the contaminated food. The illness can be life-threatening in people with weakened immune systems or infants and the elderly.

According to CNN, news of the investigation surfaced when an internal memo was accidentally sent to everyone at the FDA.

FDA spokesman Curtis Allen would not confirm or elaborate on the information, saying the memo "contains numbers of cases and hospitalizations that cannot be confirmed at this time."

"It is too early to speculate on the cause of the outbreak," Allen said.

CDC spokesperson Lola Russell told CNN ,"on initial interviews, many of the ill persons reported consuming sushi, sashimi, or similar foods in a variety of locations in the week before becoming ill."

The FDA is working with the CDC and state officials to identify the source of the outbreak. Investigators conduct interviews with sick patients about what they've eaten and analyze menus and food ingredients to trace the path of the bacteria.

The memo notes there is likely a 30-day lag time between when people become sick and when cases are reported to health officials.

Previous outbreaks of salmonella barely have been linked to bean sprouts, which are grown in warm, damp conditions.