(NEW YORK) — More than a dozen people across four states have been sickened in a salmonella outbreak linked to ground beef, the Centers for Disease Control and Prevention said.

Sixteen people in New York, New Jersey, Connecticut and Massachusetts have been sickened in the outbreak, the CDC said in an investigation notice published on Tuesday. Among those, six people have been hospitalized, it said.

All of the people who remembered the type of ground beef they ate and where they bought it reported eating 80% lean ground beef purchased from ShopRite locations in Connecticut, New Jersey and New York prior to getting sick, the CDC said. Illnesses started on dates ranging from April 27 to June 16, according to the CDC.

“Ground beef is the only common food people reported eating,” the CDC said. “Investigators are working to identify the source of the ground beef sick people ate.”

No recall has been issued and an investigation is ongoing, the CDC said.

The number of illnesses in the outbreak is likely “much higher,” as many people tend to recover from salmonella illnesses without medical care and are not tested for the bacteria, the CDC said.

Symptoms of salmonella infection include fever, diarrhea and stomach cramps and usually start six hours to six days after swallowing the bacteria. Most people recover without treatment within a week, the CDC said.

Raw, undercooked ground beef is a known source of salmonella. To avoid getting sick, ground beef should be cooked to an internal temperature of 160 degrees, according to the CDC’s Four Food Safety Steps.

Another step when shopping for ground beef, it should be separated from other foods and placed into individual plastic bags to avoid cross-contamination. It should also be stored in a leakproof container in a fridge or freezer.

The CDC also recommends any utensils, bowls and surfaces that come into contact with raw ground beef should be cleaned before being used to prepare other foods. You should also wash your hands for at least 20 seconds after preparing raw ground beef.

ABC News’ Youri Benadjaoud contributed to this report.

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