A salmonella outbreak that has sickened more than 50 people in nine states may be linked to raw tuna in sushi, ABC News said based on an investigation by the Atlanta-based Centers for Disease Control and Prevention (CDC).

The CDC noted that 53 people have been sickened, though there have been no fatalities in the outbreak. The federal health agency interviewed 36 individuals who were affected, 34 of whom reported having consumed raw tuna in sushi.

"The investigation has not conclusively identified the source of this outbreak, but most ill people interviewed reported eating sushi made with raw tuna in the week before becoming ill," the CDC said. "The investigation is ongoing and has not identified a common brand or supplier of raw tuna linked to illnesses," the agency added.

Cases have been reported in Arizona, California, Illinois, Mississippi, New Mexico, South Dakota, Virginia, Washington and Wisconsin, according to ABC News. Symptoms, which include cramps, diarrhea and fever, usually take between 12 and 72 hours to appear.

The strain of salmonella that has sickened people is called "paratyphi B" and is considered a rare form of the food-borne illness, Yahoo Health noted.

"At this time, a common brand or supplier of raw tuna has not been identified," the CDC said.

The CDC recommended that individuals who are part of certain high-risk groups should avoid raw seafood regardless of whether there is an outbreak; they include children under the age of 5; people 65 or older; and those whose immune systems are compromised in some way.

Karen Smith, the director of the California Department of Public Health, similarly alluded to the "risks (associated with) eating raw or undercooked meats, fish or poultry," according to a statement released by the agency.

"State and local health departments, including the U.S. Centers for Disease Control and Prevention and the U.S. Food and Drug Administration ... are continuing to investigate the source of the outbreak," the California Department of Public Health noted. Thirty-one of the current salmonella cases occurred in the Golden State, according to CNN.